Tüm alıştırma soruları

Soru 481Soru →

Match each patient's clinical presentation with the primary molecular mechanism of immune evasion or pathogenesis utilized by the causative organism.

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Cevap

The correct pairings are: the pregnant woman with Listeria matches phagosomal escape via cytolysin; the man with recurrent gonorrhea matches continuous alteration of surface appendages via recombination; the hemodialysis patient with Staphylococcus aureus matches binding of the IgG Fc region; and the incarcerated man with tuberculosis matches the inhibition of phagolysosome maturation.

Each pairing correctly maps a clinical scenario to the foundational virulence mechanism of the responsible pathogen. The pregnant patient with a Gram-positive motile rod is infected with Listeria monocytogenes, which uses listeriolysin O to form pores and escape the phagosome. The young man with recurrent gonorrhea lacks protective immunity because Neisseria gonorrhoeae constantly varies its pilin proteins via homologous recombination. The hemodialysis patient with coagulase-positive Staphylococcus aureus bacteremia suffers from an infection facilitated by Protein A, which binds the Fc portion of IgG to block complement activation and opsonization. Finally, the man with cavitary tuberculosis is infected by Mycobacterium tuberculosis, an organism that uses sulfatides and cord factor to inhibit EEA1, preventing phagolysosome fusion and allowing intracellular survival.

Adım Adım Çözüm

1

Identify the causative organism for each clinical vignette based on the provided history and microbiological findings.

The pathogens are Listeria monocytogenes (pregnant, unpasteurized cheese, tumbling motility), Neisseria gonorrhoeae (recurrent urethritis, intracellular diplococci), Staphylococcus aureus (catheter, coagulase-positive clusters), and Mycobacterium tuberculosis (incarceration, cavitary lesions, acid-fast bacilli).

Accurate identification of the underlying pathogen is a prerequisite for determining its specific virulence and immune evasion mechanism.

2

Determine the primary mechanism of immune evasion or pathogenesis for each identified organism.

Listeria escapes the phagosome; Neisseria alters its pili; S. aureus binds IgG via Protein A; M. tuberculosis inhibits phagolysosome fusion.

This links the foundational microbiological science to the clinical presentation, satisfying the core objective.

3

Match the pathogen's conceptual mechanism to the highly descriptive molecular text provided in the options.

Listeria pairs with cholesterol-dependent cytolysin (listeriolysin O); Neisseria pairs with homologous recombination; S. aureus pairs with surface polypeptide binding the Fc region; M. tuberculosis pairs with cell-wall glycolipids inhibiting endosomal autoantigen 1.

This completes the matching requirement by translating standard terminology into advanced molecular descriptions.

Anahtar Kavram

Successful human pathogens utilize highly specific molecular mechanisms to evade the immune system, such as escaping the phagosome (Listeria), varying surface antigens to prevent protective immunity (Neisseria), neutralizing opsonizing antibodies (Staphylococcus), and arresting intracellular clearance pathways (Mycobacterium).

Tahmini Süre:1m 30s

Soru 482Soru →

Correlate each infectious disease scenario with the specific cellular mechanism of its causative bacterial toxin.

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The correct matches pair each clinical syndrome with the distinct molecular action of its causative bacterial exotoxin: Diphtheria with EF-2 inhibition; Botulism with peripheral SNARE cleavage; Cholera with Gs-alpha activation; Tetanus with central SNARE cleavage; and Toxic Shock Syndrome with MHC-II/TCR cross-linking.

Each pathogen utilizes a distinct exotoxin with a specific molecular target. Diphtheria toxin ADP-ribosylates EF-2. Botulinum toxin cleaves SNARE proteins at the peripheral neuromuscular junction. Cholera toxin ADP-ribosylates Gs-alpha. Tetanus toxin cleaves SNARE proteins in central inhibitory interneurons. TSST-1 acts as a superantigen by cross-linking MHC-II and the T-cell receptor.

Adım Adım Çözüm

1

Analyze the clinical presentation of the 7-year-old with an unimmunized status and tonsillar exudate.

Identify the pathogen as Corynebacterium diphtheriae.

The grayish pharyngeal pseudomembrane and lack of immunization are classic for diphtheria.

2

Analyze the presentation of descending flaccid paralysis after eating home-preserved goods.

Identify the pathogen as Clostridium botulinum.

Botulism classically presents with cranial nerve palsies descending to symmetric flaccid weakness.

3

Analyze the presentation of painless, profuse watery diarrhea in an aid worker.

Identify the pathogen as Vibrio cholerae.

Cholera is characterized by voluminous 'rice-water' stools without significant inflammatory signs like fever.

4

Analyze the presentation of jaw stiffness and spastic paralysis after a puncture wound.

Identify the pathogen as Clostridium tetani.

Tetanus classically causes trismus (lockjaw) and generalized painful muscle spasms.

5

Analyze the presentation of sudden fever, rash, and hypotension associated with retained nasal packing.

Identify the pathogen as Staphylococcus aureus.

This is a classic presentation of Staphylococcal toxic shock syndrome, which can be triggered by retained foreign bodies like tampons or nasal packing.

6

Map each identified pathogen to its specific toxin mechanism.

Diphtheria = EF-2 ADP-ribosylation; Botulinum = peripheral SNARE cleavage; Cholera = Gs-alpha ADP-ribosylation; Tetanus = central SNARE cleavage; S. aureus = superantigen cross-linking.

Connecting the clinical syndrome to the foundational molecular mechanism demonstrates mastery of infectious disease pathogenesis.

Anahtar Kavram

Bacterial exotoxins utilize specific molecular mechanisms, such as ADP-ribosylation, SNARE protein cleavage, and superantigen activity, to disrupt normal host cell function and cause characteristic clinical syndromes.

Soru 483Soru →

Match each clinical and administrative scenario regarding critical decision-making with the specific legal doctrine, statute, or clinical framework that primarily governs the action taken.

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The facility advance directive screening corresponds to the Patient Self-Determination Act (PSDA). The state overriding parental refusal corresponds to the Doctrine of parens patriae. The out-of-hospital medical order honored by EMS corresponds to the Physician Orders for Life-Sustaining Treatment (POLST). The capacitated patient declining life-saving surgery corresponds to the Doctrine of informed refusal.

Each matching pairing represents a foundational intersection of clinical practice and medical law. The Patient Self-Determination Act mandates facility-level screening for advance directives. Parens patriae allows state intervention when parental decisions place a minor at risk of preventable death. The POLST paradigm provides binding, out-of-hospital medical orders for emergency personnel to withhold specific interventions in terminal illness. Informed refusal upholds patient autonomy, permitting capacitated adults to decline life-sustaining interventions.

Adım Adım Çözüm

1

Analyze the facility admission protocol scenario.

Identified as a federally mandated administrative action regarding advance directives.

The Patient Self-Determination Act (PSDA) is the specific federal legislation that requires hospitals to ask patients about advance directives at the time of admission.

2

Evaluate the pediatric treatment refusal scenario.

Identified as state intervention to protect a minor.

The legal doctrine of parens patriae allows the state to step in as a guardian to prevent parents from making medical decisions that would lead to the preventable death of a child.

3

Assess the scenario involving emergency personnel and the homebound terminal patient.

Identified as a clinical situation governed by out-of-hospital medical orders.

While Living Wills provide general preferences, only a POLST (or similar state-specific paradigm) constitutes an actionable physician order that EMS can legally follow to withhold resuscitation in the field.

4

Review the scenario of the capacitated adult declining emergency surgery.

Identified as an exercise of patient autonomy.

The Doctrine of informed refusal establishes that any patient with medical decision-making capacity has the absolute right to refuse any treatment, including life-saving measures.

Anahtar Kavram

Distinguishing core medical jurisprudence doctrines and statutory frameworks in critical and end-of-life care.

Soru 484Soru →

Match each clinical research scenario with the specific epidemiological bias or confounding principle it best describes.

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The hospital admission scenario matches Berkson paradox; the differential dropout scenario matches Attrition bias; the severity-based prescription scenario matches Confounding by indication; the indolent tumor screening scenario matches Length-time bias; and the employed control group scenario matches Healthy worker effect.

Each scenario describes a classic epidemiological phenomenon: Berkson paradox arises from hospital admission rates; attrition bias from differential study dropout; confounding by indication from prescribing practices based on severity; length-time bias from screening capturing indolent disease; and the healthy worker effect from using employed populations as controls.

Adım Adım Çözüm

1

Analyze the first scenario regarding hospital admission likelihood.

Identified as Berkson paradox.

This specific form of selection bias occurs in hospital-based studies when exposure and outcome both affect admission rates.

2

Evaluate the second scenario involving differential dropout rates.

Identified as Attrition bias.

Unequal loss to follow-up between groups selectively alters the characteristics of the remaining cohort.

3

Examine the third scenario about treatment assigned based on disease severity.

Identified as Confounding by indication.

The indication for the drug (severe disease) is associated with both the exposure and the outcome (mortality).

4

Assess the fourth scenario regarding the detection of indolent tumors.

Identified as Length-time bias.

Screening tends to catch slowly progressive diseases which naturally have better survival, creating a false impression of screening efficacy.

5

Review the fifth scenario comparing exposed workers to healthy employed workers.

Identified as Healthy worker effect.

Working populations are systematically healthier, introducing selection bias when used as a baseline for mortality or morbidity.

Anahtar Kavram

Identifying specific types of bias and confounding in epidemiological and clinical research designs.

Soru 485Soru →

For each of the described clinical scenarios, select the single most appropriate initial diagnostic imaging modality to establish the diagnosis.

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Match the pregnant patient with suspected pulmonary embolism to lower extremity compression ultrasound; the patient with a pacemaker and suspected epidural abscess to CT myelogram; the patient with suspected nephrolithiasis to non-contrast CT of the abdomen/pelvis; and the trauma patient with neck pain to non-contrast CT of the cervical spine.

Each imaging modality is chosen based on evidence-based guidelines that account for the suspected diagnosis and any specific patient contraindications. Lower extremity ultrasound prevents unnecessary radiation in pregnancy; CT myelogram circumvents MRI contraindications in pacemaker patients; non-contrast CT abdomen/pelvis optimally visualizes renal stones; and non-contrast CT cervical spine provides definitive, high-resolution trauma evaluation.

Adım Adım Çözüm

1

Evaluate the pregnant patient presenting with possible pulmonary embolism.

Identify the need to minimize radiation exposure.

Lower extremity ultrasound can diagnose a deep vein thrombosis, which is treated identically to a pulmonary embolism, safely sparing the patient from chest imaging.

2

Evaluate the patient with suspected spinal cord compression or epidural abscess.

Identify the absolute contraindication to magnetic resonance imaging.

The patient has a non-compatible pacemaker, requiring an alternative modality like CT myelogram to visualize the spinal canal.

3

Evaluate the patient with colicky flank pain and hematuria.

Recognize classic symptoms of nephrolithiasis.

Non-contrast CT is the gold standard and most appropriate initial test for identifying urinary tract stones.

4

Evaluate the patient involved in blunt trauma complaining of neck pain.

Apply cervical spine imaging guidelines.

High-risk mechanism and midline tenderness mandate imaging, and CT is superior to plain radiography in adults.

Anahtar Kavram

Appropriate selection of diagnostic imaging requires balancing modality accuracy against patient-specific contraindications, such as pregnancy or implanted medical devices.

Soru 486Soru →

Match each patient presentation to the most appropriate next step in their diagnostic evaluation based on established clinical guidelines for esophageal and swallowing disorders.

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Cevap

Patients should be matched to diagnostic studies based on the localization of their symptoms (oropharyngeal vs. esophageal) and the differentiation between structural lesions, motility disorders, and refractory functional conditions.

Appropriate test sequencing relies on characterizing the dysphagia. Oropharyngeal symptoms require dynamic imaging (modified barium swallow). Esophageal symptoms with alarm signs require direct visualization (EGD). Esophageal motility symptoms require pressure analysis (manometry). Refractory reflux without structural damage requires functional acid quantification (pH monitoring).

Adım Adım Çözüm

1

Differentiate oropharyngeal from esophageal dysphagia.

Coughing and choking immediately upon swallowing indicates an oropharyngeal etiology (requiring modified barium swallow), whereas the sensation of food getting stuck in the chest points to an esophageal etiology.

Oropharyngeal dysphagia is primarily a neuromuscular coordination issue, whereas esophageal dysphagia involves the esophageal body or lower sphincter.

2

Categorize esophageal dysphagia based on the type of food causing difficulty.

Difficulty with solids only suggests a mechanical/structural lesion, while difficulty with both solids and liquids suggests a neuromuscular motility disorder.

Liquids can easily bypass partial mechanical obstructions but fail to pass when the esophagus loses its peristaltic function or sphincter relaxation.

3

Identify alarm symptoms indicating malignancy.

The presence of significant weight loss and smoking history in the context of solid-food dysphagia prioritizes direct visualization and biopsy via EGD.

Malignant strictures must be ruled out immediately before pursuing functional studies.

4

Select appropriate functional testing for non-obstructive or refractory symptoms.

Manometry is chosen to confirm achalasia suspected on barium swallow, and pH monitoring is chosen for refractory GERD symptoms with normal anatomy.

Functional studies precisely characterize the physiologic abnormality when structural evaluation is unremarkable.

Anahtar Kavram

Diagnostic algorithm for evaluating dysphagia and esophageal disorders.

Tahmini Süre:1m 30s

Soru 487Soru →

An institutional review board is reviewing multiple research protocols. Match each proposed clinical research scenario with the epidemiological study design that best describes its methodology.

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The correct matches align each research scenario with its fundamental defining methodology regarding temporal direction and subject selection.

Each scenario accurately describes the core mechanics of its respective study design: case-control starts with disease; prospective cohort starts with present exposure; retrospective cohort starts with past exposure; cross-sectional takes a snapshot in time.

Adım Adım Çözüm

1

Analyze the first scenario regarding idiopathic pulmonary fibrosis.

Subjects are selected based on disease outcome, and researchers look backward for exposure.

This temporal relationship (outcome to exposure) defines a case-control study.

2

Analyze the second scenario regarding exercise and cardiovascular disease.

Subjects are selected based on current exposure and followed forward in real-time for disease incidence.

This forward temporal tracking from exposure defines a prospective cohort study.

3

Analyze the third scenario regarding anti-epileptic drugs and bone fractures.

Subjects are selected based on historical exposure and followed forward in historical time for disease incidence.

This reliance on existing records to track from past exposure to subsequent outcome defines a retrospective cohort study.

4

Analyze the fourth scenario regarding migraine headaches and stress.

Exposure and outcome are measured at the exact same moment in time.

The simultaneous measurement without temporal follow-up defines a cross-sectional study.

Anahtar Kavram

Epidemiological study designs are primarily distinguished by how subjects are selected (by exposure or by outcome) and the temporal relationship between the assessment of exposure and outcome.

Tahmini Süre:1m 30s

Soru 488Soru →

Match each clinical patient presentation following an acute hospitalization with the most appropriate post-acute care disposition setting based on medical necessity and rehabilitation tolerance.

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The stroke patient capable of 3 hours of therapy matches to the Inpatient Rehabilitation Facility (IRF). The ventilator-dependent patient matches to the Long-Term Acute Care Hospital (LTACH). The easily fatigued septic patient matches to the Skilled Nursing Facility (SNF). The stable, homebound heart failure patient matches to Home with Home Health Services.

Appropriate disposition depends heavily on the patient's medical complexity, required nursing care, and physical endurance. Patients requiring active, complex medical management like ventilator weaning need a Long-Term Acute Care Hospital (LTACH). Patients who need rehabilitation and can tolerate at least 3 hours of intensive daily therapy qualify for an Inpatient Rehabilitation Facility (IRF). Patients needing rehabilitation who cannot tolerate intense therapy are best suited for a Skilled Nursing Facility (SNF). Stable, homebound patients needing intermittent skilled care should receive Home with Home Health Services.

Adım Adım Çözüm

1

Evaluate the rehabilitation tolerance of patients requiring post-acute physical or occupational therapy.

The stroke patient can tolerate 3 hours of daily therapy, meeting IRF criteria. The sepsis patient fatigues at 20 minutes, failing IRF criteria and necessitating SNF placement.

Medicare guidelines strictly require patients to tolerate at least 3 hours of intensive therapy per day to qualify for an Inpatient Rehabilitation Facility.

2

Assess the medical acuity and need for daily physician intervention.

The post-ARDS patient requires active ventilator weaning and complex medical management, fitting LTACH criteria.

LTACHs are designed for patients with complex medical conditions (e.g., prolonged mechanical ventilation, severe wounds) requiring daily physician rounding and hospital-level care for an extended period.

3

Identify patients who are medically stable for a home environment but still need skilled services.

The heart failure patient is stable but needs intermittent nursing to prevent readmission, suitable for Home Health.

Home Health Services require the patient to be homebound and in need of intermittent (not continuous) skilled nursing or therapy.

Anahtar Kavram

Selecting the appropriate post-acute care setting requires matching the patient's medical complexity, nursing requirements, and physical endurance for rehabilitation to strict facility admission criteria.

Tahmini Süre:1m 30s

Soru 489Soru →

Match each clinical scenario describing a patient with an advanced malignancy who has developed acquired resistance to a targeted antineoplastic therapy with the most likely underlying molecular mechanism of resistance.

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NSCLC/osimertinib resistance matches with C797S mutation or MET amplification. CML/imatinib resistance matches with the T315I gatekeeper mutation. Melanoma/vemurafenib resistance matches with MAPK reactivation via NRAS mutation or target amplification. Prostate cancer/abiraterone resistance matches with truncated steroid receptor splice variants.

Each class of targeted therapy exerts specific selective pressure on tumor cells, leading to predictable molecular mechanisms of resistance. Recognizing these patterns is essential for sequencing next-line therapies. Osimertinib resistance occurs via C797S or bypass tracks. Imatinib resistance is driven by the T315I gatekeeper mutation. Vemurafenib resistance involves paradoxical MAPK pathway reactivation. Abiraterone resistance involves androgen receptor modifications like AR-V7.

Adım Adım Çözüm

1

Analyze the non-small cell lung cancer scenario on osimertinib.

Matches with C797S mutation or MET amplification.

Osimertinib relies on covalent binding to mutated EGFR; the C797S mutation directly disrupts this binding. Alternatively, the tumor bypasses EGFR completely via MET amplification.

2

Analyze the chronic myeloid leukemia scenario on imatinib.

Matches with the T315I gatekeeper missense mutation.

T315I is the classic structural alteration in the ABL kinase domain that blocks imatinib binding, necessitating salvage therapy with ponatinib or asciminib.

3

Analyze the melanoma scenario on vemurafenib.

Matches with reactivation of the downstream MAPK signaling cascade.

Melanoma cells overcome isolated BRAF inhibition by upregulating alternative pathway components (like NRAS), driving ERK signaling independent of the inhibited BRAF.

4

Analyze the prostate cancer scenario on abiraterone acetate.

Matches with expression of a truncated steroid receptor splice variant.

Abiraterone works by systemic androgen depletion; the tumor adapts by expressing an androgen receptor variant (AR-V7) that activates transcription even in the absence of androgen ligands.

Anahtar Kavram

Molecular mechanisms of acquired resistance to targeted antineoplastic therapies

Soru 490Soru →

Match each patient's clinical presentation and advanced hemostatic laboratory findings with the correct underlying pathophysiological mechanism of their coagulation disorder.

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The correct pairings match the time-dependent inhibitor presentation with Acquired Hemophilia A, the immediate inhibitor presentation with Lupus Anticoagulant, the sustained correction presentation with Factor XI deficiency, and the enhanced low-dose ristocetin response with Type 2B von Willebrand disease.

Each advanced laboratory finding corresponds uniquely to a specific pathophysiological mechanism. Time-dependent mixing study correction failures are driven by Factor VIII autoantibodies. Immediate mixing study failures in pro-thrombotic patients are driven by antiphospholipid antibodies. Complete, sustained mixing study corrections represent true zymogen deficiencies. Enhanced low-dose ristocetin responses point directly to the hyper-affinity glycoprotein defect of Type 2B vWD.

Adım Adım Çözüm

1

Analyze the immediate vs. incubated mixing study results to differentiate factor deficiencies from specific inhibitors.

Sustained correction indicates a factor deficiency. Immediate failure to correct indicates an immediate inhibitor. Initial correction followed by failure after 2 hours indicates a time-dependent inhibitor.

Normal plasma provides 50% factor levels, correcting a deficiency. Immediate inhibitors (like lupus anticoagulant) neutralize immediately, while Factor VIII autoantibodies require incubation at physiological temperatures to fully neutralize the factor in vitro.

2

Differentiate the clinical consequences of the specific inhibitors.

The immediate inhibitor (lupus anticoagulant) is paradoxically pro-thrombotic in vivo, explaining the recurrent fetal loss and DVT. The time-dependent inhibitor (Acquired Hemophilia A) causes severe spontaneous bleeding.

Lupus anticoagulants target phospholipid-binding proteins, causing endothelial activation in vivo. Factor VIII autoantibodies completely disrupt the intrinsic tenase complex, severely impairing in vivo hemostasis.

3

Interpret the specialized platelet aggregometry combined with the clinical presentation.

Normal coagulation times combined with thrombocytopenia and enhanced low-dose ristocetin-induced platelet aggregation (RIPA) definitively identifies Type 2B von Willebrand disease.

Unlike standard vWD which shows reduced RIPA, Type 2B involves a gain-of-function mutation. The mutant vWF spontaneously binds platelets in vivo, clearing them from circulation (causing thrombocytopenia) and reacting aggressively to even trace amounts of ristocetin in vitro.

Anahtar Kavram

Interpretation of immediate vs. incubated mixing studies and platelet aggregometry to diagnose complex coagulopathies.

Soru 491Soru →

A public health resident is reviewing various surveillance and registry reports from different medical institutions. For each provided study methodology or data collection scenario, select the specific epidemiological metric being calculated.

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Cevap

The scenarios correctly correspond to Incidence rate for the catheter-days metric, Point prevalence for the single-week survey, Attack rate for the foodborne outbreak, and Case fatality rate for the cancer death registry.

Each specific epidemiological metric matches its corresponding scenario based on the numerator and denominator used: incidence rate requires person-time, point prevalence captures a snapshot in time, attack rate applies to acute outbreaks, and case fatality rate measures lethality among diagnosed cases.

Adım Adım Çözüm

1

Analyze the first scenario regarding catheter-associated infections per 1,000 catheter-days.

The denominator involves device-time (catheter-time), indicating an incidence rate.

Incidence rate accounts for dynamic populations where individuals or devices are observed for varying lengths of time.

2

Examine the second scenario describing a survey of asthma cases during a single week.

This describes the proportion of existing cases at a single point in time, which corresponds to point prevalence.

Prevalence measures disease burden, and a 'single week' survey approximates a single point in time.

3

Review the third scenario about a foodborne illness following a specific exposure.

This is a measure of risk in a well-defined population over a short time after an exposure, known as an attack rate.

Attack rates are specialized cumulative incidence measures used in acute outbreak investigations.

4

Evaluate the fourth scenario regarding the proportion of melanoma patients who die from the disease.

This measures the lethality of the disease among diagnosed cases, which is the case fatality rate.

Case fatality rate uses the number of diagnosed cases as the denominator, unlike mortality rate which uses the general population.

Anahtar Kavram

Understanding and differentiating core measures of disease frequency based on study design, timeframes, and specific denominators.

Soru 492Soru →

During a comprehensive medical history evaluation, recognizing the association between a patient's pharmacological history and their clinical presentation is crucial for avoiding unnecessary testing and establishing an accurate diagnosis. Match each patient's medication history and symptom profile with the most likely corresponding iatrogenic diagnosis.

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Cevap

The correct associations directly link each patient's distinct clinical presentation to the known, classic adverse effect of their prescribed medication.

In each scenario, the diagnosis relies heavily on a targeted medication history. Amiodarone causes thyroid dysfunction; isotretinoin causes intracranial hypertension; allopurinol is a prime trigger for Stevens-Johnson syndrome; and ACE inhibitors classically cause a dry cough.

Adım Adım Çözüm

1

Analyze the history of the patient with atrial fibrillation.

The combination of atrial fibrillation management and new-onset hyperthyroidism points to amiodarone toxicity.

Amiodarone is a common antiarrhythmic that frequently induces thyroid dysfunction.

2

Analyze the history of the patient with severe acne.

The use of acne medication linked to papilledema indicates isotretinoin-induced idiopathic intracranial hypertension.

Vitamin A derivatives are a classic pharmacological cause of elevated intracranial pressure.

3

Analyze the history of the patient with recurrent gout.

The recent initiation of a gout medication followed by a desquamating mucosal rash is highly suggestive of allopurinol-induced Stevens-Johnson syndrome.

Allopurinol is one of the highest-risk medications for severe cutaneous adverse reactions.

4

Analyze the history of the patient with heart failure.

A new dry cough after starting heart failure therapy strongly correlates with ACE inhibitor use.

ACE inhibitors block the breakdown of bradykinin, leading to a chronic, dry cough in a significant percentage of patients.

Anahtar Kavram

Identifying medication-induced diseases during the medical history evaluation is an essential clinical skill that guides accurate diagnosis and prevents unnecessary, extensive clinical workups.

Tahmini Süre:1m 0s

Soru 493Soru →

A 46-year-old woman presents to the clinic for a routine wellness examination. Her body mass index is 33 kg/m² and her blood pressure is 138/88 mm Hg. The physician decides to initiate a discussion regarding weight management utilizing the evidence-based "5 A's" behavioral counseling framework. Arrange the following physician statements in the correct sequential order according to this protocol.

Öğeleri doğru sıraya koymak için sürükleyin

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Cevap

The correct sequence follows the 5 A's framework: Ask permission to discuss weight, Assess habits and readiness, Advise on health benefits, Agree on goals collaboratively, and Assist/Arrange by providing resources and follow-up.

The "5 A's" is an evidence-based behavioral counseling framework widely recommended for obesity management and other lifestyle interventions. The correct chronological sequence begins with 'Ask' (requesting permission to discuss the topic to respect autonomy), followed by 'Assess' (evaluating readiness, habits, and comorbidities). Once the foundation is laid, the physician should 'Advise' (provide personalized medical information and recommendations). After providing advice, the physician and patient 'Agree' (collaboratively setting realistic, measurable goals). Finally, the physician must 'Assist/Arrange' (provide resources, referrals, and schedule follow-up to support sustained change).

Adım Adım Çözüm

1

Identify the counseling framework being tested.

The scenario requires the application of the "5 A's" behavioral counseling model (Ask, Assess, Advise, Agree, Assist/Arrange).

This is a standardized, USPSTF-endorsed approach for managing obesity and lifestyle modifications.

2

Map each physician quote to its corresponding step in the framework.

Asking for permission is 'Ask'. Inquiring about habits is 'Assess'. Discussing medical benefits is 'Advise'. Setting a specific behavioral goal is 'Agree'. Providing a referral and scheduling follow-up is 'Assist/Arrange'.

Accurate identification of the communication technique ensures correct sequencing.

3

Order the mapped statements chronologically.

The correct order is Ask -> Assess -> Advise -> Agree -> Assist/Arrange.

This sequence maximizes patient engagement and minimizes resistance to change.

Anahtar Kavram

The "5 A's" (Ask, Assess, Advise, Agree, Assist) is an evidence-based behavioral counseling framework used to guide discussions on lifestyle modifications, such as weight management and smoking cessation.

Tahmini Süre:1m 30s

Soru 494Soru →

A 28-year-old primigravida at 14 weeks gestation is brought to the emergency department by her husband due to progressive confusion, lethargy, and recurrent vomiting over the past 24 hours. The husband reports that her symptoms began shortly after they attended a celebratory dinner where she consumed a large portion of steak. The patient has a lifelong history of self-restricting meat and dairy from her diet, stating they make her feel "foggy and irritable." Family history is notable for a male sibling who died at 4 days of life from a "metabolic coma."

Physical examination reveals a somnolent woman who arouses to physical stimuli. She exhibits a flapping tremor of the hands when her wrists are extended.

Laboratory studies are as follows:

Test	Result	Reference Range
Sodium	140 mEq/L	136-145 mEq/L
Potassium	4.1 mEq/L	3.5-5.0 mEq/L
Chloride	104 mEq/L	95-105 mEq/L
Bicarbonate	24 mEq/L	22-28 mEq/L
Blood urea nitrogen (BUN)	4 mg/dL	7-18 mg/dL
Creatinine	0.6 mg/dL	0.6-1.2 mg/dL
Glucose	98 mg/dL	70-99 mg/dL
Arterial pH	7.49	7.35-7.45
$PaCO_2$	28 mm Hg	35-45 mm Hg
Serum ammonia	280 μmol/L	15-45 μmol/L

Urinalysis reveals markedly elevated orotic acid levels.

Which of the following genetic principles best explains why this patient survived to adulthood while her sibling experienced early neonatal mortality?

Asymmetric epigenetic silencing of a sex chromosome during early embryogenesis

Random partition of mutant and wild-type mitochondrial genomes during mitosis

Intergenerational expansion of an unstable nucleotide repeat sequence during gametogenesis

Parent-of-origin dependent monoallelic gene expression via DNA methylation

Presence of genetically distinct cell lineages arising from a post-zygotic mutation

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Cevap: Asymmetric epigenetic silencing of a sex chromosome during early embryogenesis

Cevap

Asymmetric epigenetic silencing of a sex chromosome during early embryogenesis

The patient is experiencing an acute hyperammonemic crisis secondary to ornithine transcarbamylase (OTC) deficiency, which has been unmasked by the physiologic stress of pregnancy and a high-protein meal. OTC deficiency is the only urea cycle disorder with an X-linked recessive inheritance pattern. Males (hemizygous) typically present with severe, often fatal, neonatal hyperammonemia, consistent with the patient's deceased brother. Female carriers (heterozygous) have a highly variable clinical phenotype ranging from asymptomatic to severe adult-onset crises. This variability is driven by skewed X-chromosome inactivation (lyonization) in hepatocytes—a process of asymmetric epigenetic silencing via DNA methylation and heterochromatin formation during early embryogenesis. If by chance the normal X chromosome is preferentially inactivated in a majority of liver cells, the female carrier will exhibit limited enzyme activity and become symptomatic under nitrogen load.

Adım Adım Çözüm

1

Analyze the patient's laboratory profile and clinical presentation.

The patient has hyperammonemia, low BUN, respiratory alkalosis, and highly elevated urinary orotic acid in the setting of acute encephalopathy triggered by a high-protein meal.

These specific biochemical markers distinguish urea cycle defects from other metabolic causes of altered mental status.

2

Diagnose the specific underlying metabolic disorder.

The combination of hyperammonemia and elevated orotic acid confirms ornithine transcarbamylase (OTC) deficiency.

OTC deficiency prevents the conversion of carbamoyl phosphate and ornithine to citrulline. The accumulated carbamoyl phosphate shunts into the pyrimidine synthesis pathway, producing excess orotic acid. Other urea cycle defects (like CPS1 deficiency) present with low orotic acid.

3

Determine the genetic inheritance pattern of the identified disorder.

OTC deficiency is uniquely inherited in an X-linked recessive pattern.

Unlike all other urea cycle defects, which are autosomal recessive, OTC is X-linked. This explains the family history of a male sibling suffering lethal neonatal metabolic coma (hemizygous).

4

Identify the molecular mechanism allowing the female patient to survive to adulthood but become symptomatic under stress.

The correct mechanism is asymmetric epigenetic silencing of the X chromosome, clinically known as skewed X-inactivation or lyonization.

In heterozygous females, random X-inactivation occurs. If a disproportionately large number of normal X chromosomes are inactivated in the liver, the female will manifest symptoms of the X-linked recessive disorder, particularly when exposed to increased metabolic demand (e.g., pregnancy, high-protein diet).

Anahtar Kavram

Ornithine transcarbamylase (OTC) deficiency presentation in female carriers is dependent on the degree of skewed X-chromosome inactivation (lyonization).

Soru 495Soru →

A medical geneticist is reviewing the charts of several adult and pediatric patients with complex genetic presentations. To finalize their diagnostic formulations and targeted management plans, match each patient's clinical presentation and preliminary genetic findings to the precise underlying molecular or targeted therapeutic mechanism.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Cevabı ve açıklamayı göster

Cevap

The correct matches require linking the clinical phenotype and test results to their advanced molecular mechanisms: MSH2 loss without coding mutation matches EPCAM-induced hypermethylation; progressive ataxia with anticipation matches expansion bias during spermatogenesis; hypotonia treated with targeted therapy matches alteration of SMN2 alternative splicing; inheritance of two distinct CFTR mutations matches compound heterozygosity; and maternally inherited vision loss with variable severity matches stochastic distribution of extranuclear genomes (heteroplasmy).

Each correct pairing directly connects a complex clinical presentation to a high-yield, advanced molecular mechanism. Recognizing that EPCAM deletions epigenetically silence MSH2, that CAG repeats undergo massive expansion during spermatogenesis, that nusinersen alters SMN2 splicing, that two different variants in one gene constitute compound heterozygosity, and that mitochondrial disease severity relies on heteroplasmy are all essential competencies for diagnostic evaluation and patient counseling at the independent practitioner level.

Adım Adım Çözüm

1

Analyze the mismatch repair deficiency case (endometrial cancer with absent MSH2/MSH6).

Identify that absent protein expression without a coding mutation strongly points to epigenetic silencing, classically via upstream EPCAM deletion.

This establishes the mechanism for EPCAM-associated Lynch syndrome.

2

Analyze the progressive ataxia case demonstrating anticipation across generations.

Identify that CAG repeat disorders exhibit anticipation heavily biased toward paternal transmission due to instability during spermatogenesis.

This distinguishes polyglutamine repeat expansions from those occurring in oogenesis (like Fragile X).

3

Analyze the infant hypotonia case (SMA) receiving intrathecal therapy.

Recognize that targeted therapy for SMN1 deletion (nusinersen) modulates pre-mRNA splicing of the SMN2 paralog.

This links a modern pharmacogenomic intervention to its precise molecular mechanism of action.

4

Analyze the preconception counseling case involving cystic fibrosis.

Recognize that inheriting two completely distinct mutations in the same gene represents compound heterozygosity.

This explains why patients with the same disease may have vastly different phenotypic severities based on residual allelic function.

5

Analyze the vision loss case showing a maternal inheritance pattern with variable penetrance.

Link the variable expressivity among maternal relatives to mitochondrial heteroplasmy (random segregation of mutated mitochondrial genomes).

This explains the hallmark feature of mitochondrial disorders known as the threshold effect.

Anahtar Kavram

Advanced molecular diagnostics and targeted pharmacogenomics often rely on identifying mechanisms beyond simple Mendelian inheritance, including epigenetic silencing (EPCAM/MSH2), expansion bias during specific gametogenesis (CAG repeats in spermatogenesis), alternative splicing modulation (SMA therapy), compound heterozygosity, and mitochondrial heteroplasmy.

Soru 496Soru →

Match each bacterial pathogen's primary virulence toxin with its precise molecular mechanism of action.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Cevabı ve açıklamayı göster

Cevap

The correct matches align specific bacterial toxins with their cellular targets: Corynebacterium diphtheriae exotoxin inactivates EF-2, Vibrio cholerae enterotoxin ADP-ribosylates Gs protein, Clostridium tetani neurotoxin cleaves SNARE proteins, and Staphylococcus aureus TSST-1 cross-links TCR to MHC class II.

Each exotoxin has a highly specific cellular target that dictates its pathophysiology. Diphtheria toxin halts protein synthesis via EF-2 inactivation, causing pseudomembrane formation. Cholera toxin perpetually activates adenylate cyclase by targeting Gs, leading to secretory diarrhea. Tetanospasmin prevents the release of GABA and glycine by cleaving SNARE proteins, resulting in spastic paralysis. TSST-1 is a superantigen that bridges MHC class II and T-cell receptors without specific antigen processing, leading to toxic shock syndrome.

Adım Adım Çözüm

1

Identify the pathogen and its associated major virulence factor.

The four bacterial toxins listed are classic, well-characterized exotoxins associated with specific clinical syndromes.

Pathogen and toxin identification is the necessary first step in determining the underlying pathogenesis.

2

Recall the cellular target or molecular mechanism for each specific toxin.

Diphtheria toxin targets EF-2, cholera toxin targets Gs protein, tetanospasmin targets SNARE proteins, and TSST-1 acts as a superantigen.

Matching the molecular mechanism directly explains the distinct clinical manifestations of each bacterial infection.

Anahtar Kavram

Bacterial Exotoxin Mechanisms

Soru 497Soru →

A 28-year-old aid worker presents to a field clinic with severe, voluminous watery diarrhea and leg cramps. The responsible pathogen produces an AB-type exotoxin that causes profound fluid loss. Arrange the following steps of this toxin's cellular mechanism of action in the correct pathophysiological sequence, from initial interaction with the host cell to the ultimate physiologic effect.

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Cevabı ve açıklamayı göster

Cevap

The correct sequence of Vibrio cholerae toxin action is: 1) Binding to GM1 ganglioside, 2) Internalization of the A subunit, 3) ADP-ribosylation of the Gs protein, 4) Activation of adenylate cyclase causing increased cAMP, and 5) Activation of PKA leading to CFTR channel opening and secretory diarrhea.

The pathogenesis of Vibrio cholerae relies on its AB exotoxin. The B (binding) subunit attaches to GM1 ganglioside receptors on intestinal epithelial cells. Once endocytosed, the active A subunit escapes into the cytosol where it catalyzes the ADP-ribosylation of the Gs alpha subunit. This modification locks Gs in an active state, causing continuous stimulation of adenylate cyclase and a massive increase in intracellular cAMP. Elevated cAMP activates protein kinase A, which phosphorylates and opens the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) channel. The resulting massive efflux of chloride ions into the intestinal lumen is followed by sodium and water, producing the characteristic severe secretory diarrhea.

Adım Adım Çözüm

1

Identify the clinical syndrome and pathogen.

The presentation of severe, voluminous watery diarrhea (rice-water stools) in an aid worker points to cholera, caused by Vibrio cholerae.

Recognizing the pathogen dictates which specific AB toxin mechanism is being tested.

2

Determine the initial host-pathogen interaction.

The sequence begins with the binding of the toxin's B subunit to the GM1 ganglioside receptor.

Exotoxins must attach to specific host cell receptors before they can exert intracellular effects.

3

Trace the intracellular enzymatic cascade.

After internalization, the A subunit ADP-ribosylates the Gs protein, which turns on adenylate cyclase and increases cAMP.

This is the hallmark molecular mechanism of cholera toxin, distinguishing it from other AB toxins.

4

Identify the final cellular consequence.

Elevated cAMP activates PKA, which opens the CFTR chloride channel, dragging water into the lumen.

This terminal step directly explains the profound watery diarrhea seen in the patient.

Anahtar Kavram

Cholera toxin mechanism of action

Soru 498Soru →

A 45-year-old man undergoes a right hemicolectomy for a colon adenocarcinoma. His family history is notable for a father who died of colorectal cancer at age 49 and a sister diagnosed with endometrial cancer at age 46. The physician suspects Lynch syndrome and plans a comprehensive molecular and genetic evaluation.

Assuming this patient's cancer is ultimately found to be caused by a germline mutation in the MLH1 gene, arrange the following diagnostic and management steps in the most appropriate chronological order.

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Cevabı ve açıklamayı göster

Cevap

The correct sequence is: Tumor IHC/MSI testing -> Tumor BRAF/MLH1 methylation testing -> Germline MLH1 sequencing -> Cascade testing of relatives.

The correct sequence follows the standard molecular diagnostic algorithm for Lynch syndrome. Initial evaluation begins with tumor tissue screening via immunohistochemistry (IHC) or microsatellite instability (MSI) testing. Because loss of MLH1 is frequently caused by sporadic somatic hypermethylation of the MLH1 promoter (often correlated with a BRAF V600E mutation), tumor tissue must be tested for these somatic markers to rule out sporadic disease. Once a sporadic etiology is excluded, a peripheral blood sample is used for germline sequencing of the specific mismatch repair gene to confirm the hereditary diagnosis. Only after a specific pathogenic germline variant is definitively identified in the index patient can targeted predictive cascade testing be offered to at-risk family members.

Adım Adım Çözüm

1

Determine the initial screening test for a suspected hereditary cancer syndrome when tumor tissue is available.

Tumor immunohistochemistry (IHC) or microsatellite instability (MSI) testing is indicated.

Tumor screening identifies if the mismatch repair pathway is defective and which specific protein is involved, guiding further testing.

2

Identify the next step if MLH1 expression is lost on IHC.

Test the tumor for BRAF V600E mutation and MLH1 promoter hypermethylation.

Loss of MLH1 is most commonly due to sporadic somatic promoter hypermethylation. Testing for this (and the associated BRAF mutation) differentiates sporadic cases from true suspected Lynch syndrome.

3

Select the appropriate test to confirm the hereditary diagnosis once sporadic causes are ruled out.

Germline sequencing and deletion/duplication analysis of the MLH1 gene from a blood sample.

Germline testing confirms the presence of an inherited pathogenic variant, establishing the diagnosis of Lynch syndrome.

4

Determine the management of family members after a germline mutation is confirmed.

Targeted predictive cascade testing for the specific variant in first-degree relatives.

Once the familial mutation is known, relatives can be tested for that specific variant to determine their cancer risk and screening needs.

Anahtar Kavram

The diagnostic algorithm for Lynch syndrome requires sequential molecular testing: initial tumor screening (IHC/MSI), exclusion of sporadic causes (BRAF/methylation if MLH1 is absent), confirmatory germline sequencing, and finally, targeted cascade testing for at-risk relatives.

Tahmini Süre:1m 30s

Soru 499Soru →

A 24-year-old woman is brought to the emergency department 36 hours after intentionally ingesting a massive quantity of an unknown over-the-counter analgesic. She is visibly jaundiced and lethargic. Laboratory studies show an aspartate aminotransferase (AST) of 8,500 U/L, an alanine aminotransferase (ALT) of 9,200 U/L, and a significantly prolonged prothrombin time. A subsequent liver biopsy reveals massive centrilobular (Zone 3) parenchymal necrosis. Based on the patient's presentation, arrange the following subcellular biochemical events in the correct chronological sequence that culminated in this patient's hepatocyte injury.

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Cevap

The correct sequence is: Exhaustion of intracellular sulfhydryl-group donors -> Unopposed covalent binding of electrophilic intermediates -> Oxidative stress-induced lipid peroxidation -> Irreversible opening of the MPTP -> Efflux of cytochrome c into the cytosol.

The correct chronological progression of acetaminophen-induced hepatocellular injury begins with the depletion of protective glutathione reserves, allowing the toxic metabolite NAPQI to bind to cellular proteins. This covalent binding disrupts mitochondrial function, causing severe oxidative stress and lipid peroxidation. The resulting membrane damage triggers the irreversible opening of the mitochondrial permeability transition pore (MPTP), dissipating the mitochondrial proton gradient. Finally, this loss of integrity leads to the release of cytochrome c into the cytosol, sealing the cell's fate through both ATP-depletion necrosis and caspase-mediated apoptosis.

Adım Adım Çözüm

1

Diagnose the clinical syndrome based on the patient's presentation, laboratory values, and histological findings.

The extreme elevation of transaminases (AST/ALT in the thousands), acute coagulopathy, jaundice, and Zone 3 necrosis following an intentional analgesic overdose strongly indicate fulminant acetaminophen-induced hepatotoxicity.

Establishing the specific etiology of the injury is required to accurately identify the specific downstream pathophysiologic cellular mechanism.

2

Identify the primary molecular initiator of cellular injury in this specific toxicity model.

Acetaminophen overdose saturates normal non-toxic conjugation pathways, generating the toxic metabolite NAPQI via the CYP450 system. NAPQI immediately depletes glutathione (intracellular sulfhydryl donors).

Cellular antioxidant defenses must be exhausted before structural macromolecular injury can proceed.

3

Trace the consequence of unmitigated toxic metabolites on cellular structures.

Without glutathione, NAPQI covalently binds to cellular and mitochondrial proteins, disrupting normal mitochondrial respiration and generating reactive oxygen species (ROS) which cause lipid peroxidation.

This establishes the transition from isolated biochemical toxicity to widespread structural organelle damage.

4

Determine the final lethal mitochondrial events that execute cell death.

The extensive oxidative damage triggers the opening of the mitochondrial permeability transition pore (MPTP). The resulting loss of the proton gradient forces mitochondrial swelling, outer membrane rupture, and the release of cytochrome c to execute apoptosis and necrosis.

Understanding the terminal phase of irreversible cell injury requires linking membrane damage to the cessation of ATP synthesis and activation of executioner cascades.

Anahtar Kavram

The sequential subcellular mechanisms of chemically induced cellular injury, specifically culminating in mitochondrial dysfunction and membrane damage.

Soru 500Soru →

A 16-year-old girl is brought to the clinic by her parents for a follow-up examination. She has a history of mild intellectual disability, truncal obesity, and obsessive food-seeking behavior. As an infant, she exhibited severe central hypotonia and poor feeding that required temporary nasogastric tube support. Physical examination today reveals a body mass index (BMI) of 34 kg/m² along with a narrow biparietal diameter, almond-shaped eyes, and small hands and feet.

To confirm the clinically suspected diagnosis, targeted molecular genetic testing is performed. DNA methylation analysis of the 15q11-q13 region is abnormal, showing an exclusively maternal methylation pattern. Subsequent high-resolution chromosomal microarray analysis demonstrates no evidence of genomic microdeletions or duplications across the genome.

Which of the following is the most likely underlying genetic mechanism responsible for this patient's condition?

Inheritance of two structurally intact homologous chromosomes from a single parent

Interstitial microdeletion on the paternally inherited chromosome

Defective post-zygotic mitotic segregation leading to somatic mosaicism

Trinucleotide repeat expansion in the untranslated region of a maternal gene

De novo point mutation in the ubiquitin protein ligase E3A gene

Cevabı ve açıklamayı göster

Cevap: Inheritance of two structurally intact homologous chromosomes from a single parent

Cevap

The correct answer is the inheritance of two structurally intact homologous chromosomes from a single parent, describing maternal uniparental disomy.

The patient's clinical presentation is classic for Prader-Willi syndrome (PWS). The diagnosis is confirmed by abnormal DNA methylation analysis of the 15q11-q13 region, which shows only a maternally imprinted pattern, indicating an absence of functional paternally expressed genes. While the most common cause of PWS is a paternal microdeletion (approximately 70% of cases), this patient has a completely normal chromosomal microarray. Because microarrays detect copy number variations, a normal result explicitly rules out a deletion. The second most common cause of PWS (approximately 25-30% of cases) is maternal uniparental disomy (UPD). In maternal UPD, the offspring inherits two copies of chromosome 15 from the mother and zero copies from the father. Because both chromosomes are of maternal origin, they both carry the maternal imprint (which silences the genes critical for preventing PWS), leading to a complete absence of expression of these specific genes despite the chromosomes being structurally intact. Therefore, the inheritance of two structurally intact homologous chromosomes from a single parent is the correct mechanism.

Adım Adım Çözüm

1

Identify the clinical syndrome based on the patient's history and physical examination findings.

The combination of infantile hypotonia, childhood hyperphagia, truncal obesity, mild intellectual disability, and characteristic facies strongly points to Prader-Willi syndrome (PWS).

Recognizing the phenotype establishes the differential diagnosis and directs the interpretation of specific genetic tests.

2

Analyze the DNA methylation assay results.

The presence of an exclusively maternal methylation pattern at 15q11-q13 confirms the diagnosis of PWS by demonstrating the lack of a functional paternally imprinted allele.

Methylation testing is highly sensitive for PWS but does not identify the specific molecular mechanism (deletion, uniparental disomy, or imprinting center defect).

3

Integrate the chromosomal microarray results to deduce the specific genetic mechanism.

The microarray shows no genomic microdeletions. Therefore, the lack of paternal expression must be due to the presence of two maternal copies of chromosome 15 (maternal uniparental disomy).

Microarray analysis detects copy number variations. A normal result rules out the most common cause of PWS (paternal microdeletion), isolating uniparental disomy or an imprinting defect as the cause.

Anahtar Kavram

Molecular mechanisms and diagnostic test interpretation in Prader-Willi syndrome.

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