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Question 1801Question →

Match each distinct arterial pulse contour abnormality observed on physical examination to its most closely associated underlying cardiovascular pathology.

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Items

Weak and delayed arterial pulse with a slow upstroke (pulsus parvus et tardus)
Rapid, bounding arterial pulse with a quick upstroke and sudden collapse (water-hammer pulse)
Alternating strong and weak arterial pulse beats despite a regular cardiac rhythm (pulsus alternans)
An arterial pulse with two distinct palpable systolic peaks per cardiac cycle (pulsus bisferiens)

Matches

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Answer

The correct pairings match pulsus parvus et tardus with Aortic stenosis, the water-hammer pulse with Aortic regurgitation, pulsus alternans with Severe left ventricular systolic dysfunction, and pulsus bisferiens with Hypertrophic cardiomyopathy.
Each arterial pulse contour provides immediate, non-invasive clues about a patient's stroke volume, ejection velocity, and vascular resistance. Recognizing these distinct patterns aids in differentiating structural valvular defects, such as stenosis versus regurgitation, and functional myocardial abnormalities, such as severe heart failure or outflow tract obstruction.

Step-by-Step Solution

1
Analyze the first finding: Weak and delayed arterial pulse (pulsus parvus et tardus).
Identify as characteristic of Aortic stenosis.
The narrowed aortic valve area restricts forward flow, causing a slow rise in the arterial pulse wave and a diminished peak amplitude.
2
Analyze the second finding: Rapid, bounding pulse with sudden collapse (water-hammer pulse).
Identify as characteristic of Aortic regurgitation.
A high stroke volume rapidly ejected into the aorta followed by swift regurgitant backflow into the ventricle creates an unusually wide pulse pressure.
3
Analyze the third finding: Alternating strong and weak beats (pulsus alternans).
Identify as a sign of Severe left ventricular systolic dysfunction.
The failing myocardium cannot maintain a consistent stroke volume, leading to beat-to-beat variations in the strength of the arterial pulsation.
4
Analyze the fourth finding: Pulse with two systolic peaks (pulsus bisferiens).
Identify as characteristic of Hypertrophic cardiomyopathy.
A strong initial ejection is quickly interrupted by mid-systolic septal obstruction of the outflow tract, creating two distinct palpable peaks during systole.

Key Concept

Correlation of abnormal arterial pulse waveforms with specific underlying hemodynamic and structural cardiac derangements.
Question 1802Question →

Match the following endocrine laboratory profiles with their most likely underlying pathophysiologic diagnosis.

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Items

Primary adrenal insufficiency
Secondary adrenal insufficiency
Cushing disease
Ectopic ACTH syndrome

Matches

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Answer

Primary adrenal insufficiency matches with elevated ACTH, low cortisol, high renin, and low aldosterone. Secondary adrenal insufficiency matches with low ACTH, low cortisol, normal renin, and normal aldosterone. Cushing disease matches with elevated ACTH, high cortisol, and successful high-dose dexamethasone suppression. Ectopic ACTH syndrome matches with very high ACTH, high cortisol, severe hypokalemia, and failure of high-dose dexamethasone suppression.
The correct matches align the pathophysiology of the adrenal axis with the expected laboratory results. Primary failures affect all cortical zones, elevating trophic hormones like ACTH and renin. Secondary failures affect only ACTH-dependent zones. Cushing disease retains some feedback sensitivity, while ectopic sources do not.

Step-by-Step Solution

1
Analyze the cortisol and ACTH levels to determine if the pathology is a state of hypercortisolism or hypocortisolism, and whether it is ACTH-dependent or ACTH-independent.
Cortisol and ACTH profiles separate the profiles into two hypocortisolism states and two hypercortisolism states.
This is the primary branch point in evaluating adrenal cortex disorders.
2
For the hypocortisolism states, evaluate the mineralocorticoid axis (aldosterone and plasma renin activity).
Abnormal aldosterone and renin indicate primary adrenal failure, while normal aldosterone and renin indicate a secondary (pituitary) etiology.
Aldosterone is regulated by the renin-angiotensin-aldosterone system, which remains intact if only the pituitary fails.
3
For the ACTH-dependent hypercortisolism states, evaluate the response to the high-dose dexamethasone suppression test.
Suppression indicates a pituitary adenoma (Cushing disease), while a lack of suppression indicates an ectopic ACTH source.
Pituitary adenomas retain partial negative feedback mechanisms, whereas ectopic tumors are completely autonomous.

Key Concept

Differentiating adrenal cortex disorders based on hypothalamic-pituitary-adrenal axis feedback and mineralocorticoid regulation.
Question 1803Question →

Match each clinical presentation to the most likely hepatobiliary or metabolic liver diagnosis.

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Items

A middle-aged female with insidious onset of pruritus, fatigue, xanthelasma, and elevated alkaline phosphatase. Serology shows anti-mitochondrial antibodies.
A young adult male with a history of bloody diarrhea presents with fatigue and elevated alkaline phosphatase. MRCP reveals alternating strictures and dilations of the bile ducts.
A young female with amenorrhea, fatigue, and jaundice. Labs reveal AST 850 U/L, ALT 920 U/L, elevated IgG levels, and positive anti-smooth muscle antibodies.
A middle-aged man with bronze skin pigmentation, recent-onset diabetes mellitus, hepatomegaly, and arthropathy involving the second and third metacarpophalangeal joints.
A young adult male with new-onset resting tremor, dysarthria, mildly elevated liver enzymes, and decreased serum ceruloplasmin levels.

Matches

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Answer

The correct pairings are: the middle-aged female with pruritus and AMA matches with Primary biliary cholangitis; the young male with bloody diarrhea and beaded bile ducts matches with Primary sclerosing cholangitis; the young female with transaminitis and anti-smooth muscle antibodies matches with Autoimmune hepatitis; the middle-aged man with bronze diabetes matches with Hereditary hemochromatosis; and the young male with tremor and low ceruloplasmin matches with Wilson disease.
Each specific clinical vignette provides pathognomonic features for a distinct liver pathology. Recognizing demographic risk factors (e.g., female gender in PBC, young males in PSC), characteristic serologies (AMA, ASMA), and unique systemic findings (neurologic deficits in Wilson disease, bronze diabetes in hemochromatosis) allows for accurate pairing with the underlying hepatobiliary or metabolic disease.

Step-by-Step Solution

1
Identify the primary mechanism of liver injury in each vignette.
Vignettes 1 and 2 show a cholestatic pattern (elevated alkaline phosphatase), vignette 3 shows a hepatocellular pattern (high AST/ALT), and vignettes 4 and 5 show systemic metabolic derangements.
Categorizing the pattern of liver injury significantly narrows the differential diagnosis.
2
Analyze specific serologic and demographic markers for the autoimmune etiologies.
Anti-mitochondrial antibodies correlate with primary biliary cholangitis; anti-smooth muscle antibodies correlate with autoimmune hepatitis; history of bloody diarrhea (ulcerative colitis) correlates with primary sclerosing cholangitis.
These associations are highly specific and often pathognomonic for their respective autoimmune liver diseases.
3
Differentiate the metabolic liver diseases based on systemic manifestations.
Bronze diabetes and metacarpophalangeal arthropathy map to iron overload (hemochromatosis), while resting tremor and low ceruloplasmin map to copper overload (Wilson disease).
Metabolic storage diseases accumulate in specific organs, leading to characteristic phenotypic presentations.

Key Concept

Clinical and serological diagnosis of autoimmune and metabolic liver diseases
Question 1804Question →

Match each clinical presentation with the most appropriate, guideline-directed primary antimicrobial therapy.

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Items

A 24-year-old pregnant woman in her first trimester presents with an expanding erythematous targetoid rash and mild fatigue after a recent camping trip.
A 65-year-old man develops profuse, foul-smelling watery diarrhea and marked leukocytosis two weeks after completing treatment for community-acquired pneumonia.
A 30-year-old man presents with a solitary, painless, indurated penile ulcer and bilateral inguinal lymphadenopathy; non-treponemal serology is reactive.
A 45-year-old woman with a history of injection drug use presents with high fever, a new holosystolic murmur, and blood cultures yielding methicillin-susceptible Staphylococcus aureus.
A 19-year-old college student presents with sudden-onset fever, headache, nuchal rigidity, and a rapidly spreading petechial rash; cerebrospinal fluid analysis reveals Gram-negative diplococci.

Matches

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Answer

Lyme disease in pregnancy matches with oral amoxicillin; Clostridioides difficile infection matches with oral fidaxomicin; primary syphilis matches with intramuscular penicillin G benzathine; MSSA endocarditis matches with intravenous cefazolin; meningococcal meningitis matches with intravenous ceftriaxone.
Each patient presentation maps to a specific, guideline-directed antimicrobial agent. Amoxicillin is safe for Lyme disease in pregnancy. Fidaxomicin is the preferred initial treatment for C. difficile. Penicillin G benzathine is the definitive therapy for primary syphilis. Cefazolin is superior for MSSA endocarditis. Ceftriaxone provides necessary CNS penetration for meningococcal meningitis.

Step-by-Step Solution

1
Analyze the first patient's targetoid rash and pregnant status.
Identifies early localized Lyme disease requiring pregnancy-safe antibiotics.
Doxycycline is teratogenic, making amoxicillin the safest effective choice.
2
Evaluate the second patient's post-antibiotic diarrhea.
Identifies an initial episode of Clostridioides difficile infection.
Current guidelines recommend oral fidaxomicin over vancomycin for primary episodes to decrease recurrence.
3
Assess the third patient's painless penile ulcer and reactive serology.
Diagnoses primary syphilis.
Treponema pallidum remains exquisitely sensitive to penicillin G benzathine.
4
Recognize the fourth patient's presentation of right-sided infective endocarditis.
Identifies MSSA endocarditis.
Requires beta-lactam therapy such as intravenous cefazolin for optimal bactericidal activity.
5
Diagnose the fifth patient's petechial rash and Gram-negative diplococci in CSF.
Identifies meningococcal meningitis.
Requires a third-generation cephalosporin like intravenous ceftriaxone for effective central nervous system penetration.

Key Concept

Targeted antimicrobial selection based on pathogen profile, site of infection, and host factors.
Question 1805Question →

Match each characteristic urinalysis sediment finding with its most likely underlying renal pathology.

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Items

Pigmented 'muddy brown' granular casts and epithelial cell casts
Dysmorphic red blood cells and red blood cell casts
White blood cell casts, sterile pyuria, and eosinophiluria
Fatty casts and oval fat bodies with a 'Maltese cross' appearance under polarized light

Matches

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Answer

The correct pairings link muddy brown casts to acute tubular necrosis, dysmorphic red blood cells to acute glomerulonephritis, white blood cell casts with eosinophiluria to acute interstitial nephritis, and fatty casts to nephrotic syndrome.
Each urinalysis sediment pattern reflects a distinct pathophysiological process in the kidney. Granular casts form from necrotic tubular cells (ATN). RBC casts form from glomerular bleeding (nephritic syndrome). WBC casts with eosinophils reflect interstitial allergic inflammation (AIN). Fatty casts reflect severe hyperlipidemia and lipiduria secondary to profound proteinuria (nephrotic syndrome).

Step-by-Step Solution

1
Analyze the urinalysis finding of 'muddy brown' granular casts.
Matches with Acute tubular necrosis.
These casts are formed from necrotic tubular epithelial cells sloughing into the tubular lumen due to ischemic or toxic injury.
2
Analyze the finding of dysmorphic red blood cells and red blood cell casts.
Matches with Acute glomerulonephritis.
Dysmorphic RBCs and casts signify bleeding of glomerular origin, which occurs when inflammation disrupts the glomerular basement membrane.
3
Analyze the finding of white blood cell casts, sterile pyuria, and eosinophiluria.
Matches with Acute interstitial nephritis.
WBC casts indicate inflammation in the kidney itself (unlike simple cystitis), and eosinophils strongly suggest an allergic hypersensitivity reaction in the interstitium.
4
Analyze the finding of fatty casts and oval fat bodies.
Matches with Nephrotic syndrome.
Significant lipiduria occurs alongside massive proteinuria due to altered glomerular permeability and compensatory hepatic lipid synthesis.

Key Concept

Correlation of urinalysis sediment findings with specific renal pathologies
Question 1806Question →

A gastroenterology clinic regularly screens and evaluates patients for viral hepatitis. Proper interpretation of Hepatitis B serologic panels is critical for determining the phase of infection and appropriate management. Match each of the following patient Hepatitis B serologic profiles with the most appropriate clinical interpretation.

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Items

Profile A: HBsAg (+), Anti-HBc IgM (+), HBeAg (+), Anti-HBs (-)
Profile B: HBsAg (-), Anti-HBc IgG (+), HBeAg (-), Anti-HBs (+)
Profile C: HBsAg (-), Anti-HBc (-), HBeAg (-), Anti-HBs (+)
Profile D: HBsAg (+), Anti-HBc IgG (+), HBeAg (-), Anti-HBs (-)

Matches

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Answer

Profile A corresponds to acute hepatitis B infection (highly infectious); Profile B corresponds to resolved prior infection (natural immunity); Profile C corresponds to immunity from vaccination; Profile D corresponds to chronic hepatitis B infection (inactive carrier state).
Matching each Hepatitis B serology profile to its correct clinical state relies on evaluating the presence of specific antigens and antibodies. HBsAg indicates active infection. Anti-HBc distinguishes natural exposure (positive) from vaccination (negative), with IgM marking acute disease and IgG marking chronic or past disease. Anti-HBs represents protective immunity, and HBeAg signifies high viral replication and infectivity.

Step-by-Step Solution

1
Evaluate the HBsAg (Surface Antigen) status.
Determines if the patient currently has the virus in their blood.
HBsAg is the primary hallmark of an active infection, whether in the acute or chronic phase.
2
Evaluate the Anti-HBc (Core Antibody) status and subtype (IgM vs. IgG).
Differentiates between acute infection (IgM), chronic or resolved infection (IgG), and vaccination (negative).
The core antigen is not present in the standard Hepatitis B vaccine, meaning Anti-HBc only develops after exposure to the natural virus.
3
Evaluate the Anti-HBs (Surface Antibody) status.
Determines if the patient has successfully achieved immunity.
Anti-HBs develops only after successful clearance of a natural infection or as an intended immune response to vaccination.
4
Evaluate the HBeAg (Envelope Antigen) status.
Determines the level of active viral replication and degree of infectivity.
HBeAg is a surrogate marker for active viral replication; its presence indicates a highly infectious state, whereas its absence in a chronic carrier points toward lower infectivity.

Key Concept

Interpretation of Hepatitis B serologic markers to determine infection phase and immunity status.
Question 1807Question →

Match the following classic electrocardiographic (ECG) findings with their most likely underlying structural or electrophysiologic pathology.

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Items

Diffuse ST-segment elevations with reciprocal ST depression in leads aVR and V1, accompanied by PR-segment depression
Electrical alternans characterized by varying amplitudes of the QRS complex from beat to beat
Progressive lengthening of the PR interval culminating in a non-conducted P wave and a dropped QRS complex
Shortened PR interval, widened QRS complex, and a slurred initial upstroke of the QRS complex

Matches

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Answer

Diffuse ST elevations pair with inflammation of the fibroserous sac (acute pericarditis). Electrical alternans pairs with fluid accumulation causing pendular motion (cardiac tamponade). Progressive PR lengthening pairs with reversible atrioventricular node block (Mobitz Type I). A shortened PR interval with a slurred upstroke pairs with an accessory electrical pathway (Wolff-Parkinson-White syndrome).
Each classic ECG finding reliably reflects a specific structural or electrophysiological disruption. Epicardial inflammation causes diffuse repolarization abnormalities. Massive pericardial fluid creates a mechanical swinging effect altering ECG voltages. AV node disease causes progressive conduction delay. Finally, an accessory pathway creates a secondary, faster route for ventricular depolarization.

Step-by-Step Solution

1
Analyze the first ECG finding: Diffuse ST elevations and PR depressions.
Identified as the pathognomonic pattern for acute pericarditis.
Widespread ST elevation without corresponding vascular territory localizing signs indicates diffuse epicardial injury from sac inflammation.
2
Analyze the second ECG finding: Electrical alternans.
Identified as a classic sign of cardiac tamponade.
The varying height of the QRS complex is a mechanical artifact created by the heart swinging closer to and further from the chest wall leads within a massive pericardial effusion.
3
Analyze the third ECG finding: Progressive PR prolongation leading to a dropped beat.
Identified as Mobitz Type I (Wenckebach) second-degree heart block.
This pattern reflects progressive fatigue and delayed conduction, which anatomically occurs at the AV node.
4
Analyze the fourth ECG finding: Short PR interval with a delta wave.
Identified as ventricular pre-excitation (Wolff-Parkinson-White syndrome).
Electrical signals bypass the AV node's normal delay via an accessory pathway, exciting the ventricles early and causing the wide, slurred QRS complex.

Key Concept

Correlation of pathognomonic electrocardiographic findings with their specific underlying cardiovascular pathophysiology.
Question 1808Question →

A genetics consultation service is reviewing several patient charts for familial endocrine disorders. Based on the clinical descriptions provided below, match each patient's presentation with the most likely underlying genetic syndrome.

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Items

A 28-year-old with recurrent calcium oxalate nephrolithiasis, refractory peptic ulcer disease, and bilateral temporal hemianopia.
A 35-year-old with episodic diaphoresis and tachycardia, elevated serum calcium, and a calcitonin-secreting thyroid nodule.
A 19-year-old with a tall and slender build, painless submucosal nodules on the lips and tongue, and severe paroxysmal hypertension.
A 12-year-old with chronic oral candidiasis, a positive Chvostek sign, and new-onset postural hypotension with generalized hyperpigmentation.

Matches

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Answer

Patient 1 matches with MEN 1; Patient 2 matches with MEN 2A; Patient 3 matches with MEN 2B; Patient 4 matches with Autoimmune polyendocrine syndrome type 1.
Each syndrome presents with a specific triad or cluster of clinical features. MEN 1 features parathyroid, pancreatic, and pituitary tumors. MEN 2A features medullary thyroid cancer, pheochromocytoma, and parathyroid hyperplasia. MEN 2B features medullary thyroid cancer, pheochromocytoma, mucosal neuromas, and marfanoid habitus. APS-1 features chronic mucocutaneous candidiasis, hypoparathyroidism, and Addison disease.

Step-by-Step Solution

1
Analyze Patient 1's symptoms of nephrolithiasis, peptic ulcer disease, and temporal hemianopia.
Identified as primary hyperparathyroidism, a gastrinoma, and a pituitary adenoma.
These three pathologies define the '3 Ps' (Parathyroid, Pancreas, Pituitary) of Multiple endocrine neoplasia type 1.
2
Evaluate Patient 2's symptoms of episodic tachycardia, hypercalcemia, and an elevated calcitonin level.
Identified as a pheochromocytoma, primary hyperparathyroidism, and medullary thyroid cancer.
This combination exactly matches the clinical triad of Multiple endocrine neoplasia type 2A.
3
Assess Patient 3's tall build, mucosal nodules, and paroxysmal hypertension.
Identified as marfanoid habitus, mucosal neuromas, and a pheochromocytoma.
These physical and clinical findings uniquely indicate Multiple endocrine neoplasia type 2B.
4
Review Patient 4's fungal infections, positive Chvostek sign, and hyperpigmentation.
Identified as chronic candidiasis, hypoparathyroidism, and primary adrenal insufficiency.
Recognizing this classic autoimmune destruction sequence points directly to Autoimmune polyendocrine syndrome type 1 (APS-1).

Key Concept

Clinical recognition of multiple endocrine neoplasia (MEN) syndromes and autoimmune polyendocrine syndromes based on combinations of distinct endocrine tumors and autoimmune diseases.
Estimated Time:1m 30s
Question 1809Question →

A physician is reviewing several cases of suspected infective endocarditis. The causative microorganisms often have distinct clinical associations based on patient demographics and antecedent procedures. For each patient presentation described below, identify the most probable responsible pathogen.

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Items

A 32-year-old with a history of injection drug use, presenting with high fever, a tricuspid regurgitation murmur, and cavitary lung lesions.
A 65-year-old with urinary retention who develops a new systolic murmur and fever three weeks following a cystoscopy.
A 48-year-old with severe gingivitis who develops subacute fevers and Osler nodes one month after a deep dental scaling procedure.
A 58-year-old who develops a paravalvular leak and persistent bacteremia one month following mechanical mitral valve replacement.
A 70-year-old presenting with insidious endocarditis who is subsequently diagnosed with asymptomatic ascending colon adenocarcinoma.

Matches

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Answer

The correct matches rely on identifying the specific risk factor for each pathogen: injection drug use (Staphylococcus aureus), genitourinary instrumentation (Enterococcus faecalis), dental work (Viridans group streptococci), recent prosthetic valves (Staphylococcus epidermidis), and colonic malignancy (Streptococcus gallolyticus).
Each pathogen presents with distinct epidemiological associations. Staphylococcus aureus causes acute, right-sided endocarditis in IV drug users. Enterococcus faecalis often follows GU tract manipulation. Viridans group streptococci are tied to poor dentition and dental procedures. Staphylococcus epidermidis is the leading cause of early prosthetic valve infections. Streptococcus gallolyticus is highly associated with colonic lesions.

Step-by-Step Solution

1
Identify the primary risk factor or underlying condition in each clinical scenario.
The distinct risk factors provided are: intravenous drug use, genitourinary instrumentation, dental procedure, prosthetic valve presence, and colorectal malignancy.
Endocarditis pathogens have highly specific associations with certain portals of entry and patient demographics.
2
Correlate each risk factor with the normal flora of the affected site or the typical nosocomial exposure.
Skin and IV access correlates with Staphylococcus aureus; GI tract pathology with Streptococcus gallolyticus; oral cavity with Viridans group streptococci; GU tract with Enterococcus faecalis; and surgical hardware with Staphylococcus epidermidis.
Pathogens typically enter the bloodstream through the disruption of mucosal or cutaneous barriers where they naturally colonize.

Key Concept

Infective Endocarditis Microbiology and Risk Factors
Question 1810Question →

Match the following structural heart diseases with their characteristic dynamic auscultation findings elicited during physical maneuvers.

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Items

Hypertrophic obstructive cardiomyopathy
Mitral valve prolapse
Valvular aortic stenosis
Mitral regurgitation

Matches

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Answer

Hypertrophic obstructive cardiomyopathy corresponds to the murmur that becomes louder with Valsalva strain; Mitral valve prolapse corresponds to the click moving closer to S1S_1 upon sudden standing; Valvular aortic stenosis corresponds to the murmur that becomes softer with isometric handgrip; Mitral regurgitation corresponds to the murmur that becomes louder with isometric handgrip.
Dynamic maneuvers are essential for distinguishing cardiac murmurs by predictably altering hemodynamics. Decreased preload (from the Valsalva maneuver or standing) reduces left ventricular volume, which intensifies the hypertrophic obstructive cardiomyopathy murmur by worsening the outflow obstruction, and causes an earlier click in mitral valve prolapse. Conversely, increased afterload (from isometric handgrip) elevates aortic pressure, which softens the aortic stenosis murmur by decreasing the forward pressure gradient, but intensifies the mitral regurgitation murmur by driving more backward flow.

Step-by-Step Solution

1
Analyze the maneuvers that decrease left ventricular preload (Valsalva strain, sudden standing).
These maneuvers decrease venous return, resulting in a smaller left ventricular chamber size.
To understand their specific effects on volume-dependent dynamic murmurs such as hypertrophic obstructive cardiomyopathy and mitral valve prolapse.
2
Match the preload-dependent pathologies to their corresponding clinical findings.
In hypertrophic obstructive cardiomyopathy, reduced chamber volume worsens the dynamic obstruction, increasing the murmur. In mitral valve prolapse, reduced volume causes the redundant leaflets to prolapse earlier, moving the click closer to S1S_1.
Correctly pairs the first two structural diseases with their physiological responses.
3
Analyze the maneuvers that increase left ventricular afterload (isometric handgrip).
Isometric handgrip primarily increases systemic vascular resistance and aortic pressure.
To determine its divergent effects on fixed stenotic versus regurgitant valvular lesions.
4
Match the afterload-dependent pathologies to their corresponding clinical findings.
In aortic stenosis, increased aortic pressure reduces the forward transvalvular gradient, softening the murmur. In mitral regurgitation, increased systemic resistance forces more blood backward into the left atrium, increasing the murmur intensity.
Correctly pairs the remaining two structural diseases with their physiological responses.

Key Concept

The physiological effects of dynamic auscultation maneuvers (preload and afterload alterations) on the intensity and timing of cardiac murmurs.
Estimated Time:1m 30s
Question 1811Question →

Evaluate the following diagnostic test patterns evaluating the hypothalamic-pituitary-adrenal (HPA) axis and pair each biochemical profile with the most likely underlying etiology.

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Items

Pituitary corticotroph adenoma (Cushing disease)
Ectopic ACTH-secreting tumor
Unilateral adrenal adenoma
Autoimmune adrenalitis
Chronic exogenous prednisone therapy

Matches

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Answer

The biochemical profiles correctly match the etiologies based on ACTH dependency and the presence or absence of HPA axis feedback inhibition during dynamic testing.
Proper localization of adrenal pathologies requires interpreting the negative feedback loop. ACTH-dependent hypercortisolism (high ACTH) is differentiated using high-dose dexamethasone; pituitary sources retain partial feedback sensitivity and suppress, while ectopic sources do not. ACTH-independent hypercortisolism (low ACTH) points directly to an adrenal source. In hypocortisolism, elevated ACTH indicates primary adrenal failure (Addison's), whereas suppressed ACTH points to central causes or exogenous suppression.

Step-by-Step Solution

1
Analyze the baseline ACTH and cortisol levels for each profile.
Categorizes the condition as ACTH-dependent, ACTH-independent, or a primary failure of the adrenal gland.
ACTH dependency is the primary branch point in localizing HPA axis pathology.
2
Evaluate the response to dynamic testing, such as dexamethasone suppression or cosyntropin stimulation.
Differentiates between pituitary and ectopic sources of ACTH, and confirms primary versus secondary adrenal insufficiency.
Dynamic testing assesses the integrity of the negative feedback loop and glandular responsiveness.
3
Correlate the combined static and dynamic lab findings with the specific pathophysiologic etiology.
Accurately pairs each laboratory profile with its underlying clinical diagnosis.
Each etiology possesses a unique biochemical signature.

Key Concept

Hypothalamic-Pituitary-Adrenal (HPA) axis evaluation and localization using static ACTH/cortisol levels and dynamic suppression/stimulation testing.
Estimated Time:1m 30s
Question 1812Question →

A series of patients undergo evaluation for various nephritic and nephrotic syndromes. Based on the underlying pathophysiologic mechanisms, match each specific glomerular disease with its characteristic defining renal biopsy finding.

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Items

Poststreptococcal glomerulonephritis
IgA nephropathy
Membranous nephropathy
Minimal change disease
Goodpasture syndrome

Matches

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Answer

The correct matches align each specific glomerular pathology with its classic immunofluorescence or electron microscopy pattern: Poststreptococcal glomerulonephritis pairs with subepithelial 'humps'; IgA nephropathy pairs with mesangial immune deposition; Membranous nephropathy pairs with subepithelial 'spikes'; Minimal change disease pairs with podocyte effacement; and Goodpasture syndrome pairs with linear IgG deposition.
Each glomerular disease has a unique pathophysiology that dictates its presentation on renal biopsy. Poststreptococcal glomerulonephritis features subepithelial humps due to heavy immune complex deposition. IgA nephropathy is characterized specifically by mesangial IgA immune deposits. Membranous nephropathy displays a 'spike and dome' pattern secondary to subepithelial deposits and subsequent basement membrane thickening. Minimal change disease shows normal light microscopy but diffuse podocyte effacement on electron microscopy. Goodpasture syndrome is an autoimmune disease driven by anti-GBM antibodies, leading to a smooth, linear immunofluorescence pattern rather than a granular one.

Step-by-Step Solution

1
Categorize each glomerular disease into its primary clinical presentation (nephritic versus nephrotic).
Poststreptococcal, IgA nephropathy, and Goodpasture syndrome are typically nephritic. Membranous nephropathy and Minimal change disease are typically nephrotic.
Establishing the clinical syndrome helps narrow down the expected pathophysiologic mechanisms.
2
Identify the type of immune complex deposition or structural damage associated with each disease.
Poststreptococcal = circulating immune complexes (granular, humps); IgA = mesangial complexes; Membranous = in situ subepithelial complexes (spikes); Minimal change = podocyte cytokine damage (effacement); Goodpasture = anti-GBM antibodies (linear).
The precise location and nature of the immune attack or structural damage directly correlate with the biopsy findings.
3
Map the pathophysiologic mechanisms to the provided microscopic descriptions.
Each disease is successfully matched to its pathognomonic biopsy feature.
Ensures accurate correlation of theoretical pathogenesis with practical diagnostic pathology.

Key Concept

Pathological evaluation of glomerular diseases relies on identifying specific patterns of immune complex deposition (linear vs. granular, subepithelial vs. mesangial), cellular proliferation, and ultrastructural podocyte changes on biopsy.
Estimated Time:1m 30s
Question 1813Question →

Match each clinical presentation and characteristic high-resolution esophageal manometry finding to the most appropriate esophageal motility disorder.

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Items

Progressive dysphagia to solids and liquids; manometry reveals absent esophageal peristalsis and incomplete lower esophageal sphincter (LES) relaxation.
Intermittent noncardiac chest pain and dysphagia; manometry reveals premature, simultaneous distal esophageal contractions with normal LES relaxation.
Severe chronic gastroesophageal reflux and dysphagia; manometry reveals absent peristalsis in the lower two-thirds of the esophagus and profoundly decreased LES resting pressure.
Intense episodic retrosternal chest pain; manometry reveals extreme high-amplitude, prolonged peristaltic contractions with normal LES relaxation.

Matches

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Answer

Absent peristalsis/incomplete LES relaxation matches with Achalasia; premature/simultaneous contractions matches with Distal esophageal spasm; absent lower peristalsis/low LES pressure matches with Systemic sclerosis; extreme high-amplitude contractions matches with Hypercontractile esophagus.
Each motility disorder possesses a distinct manometric signature. Achalasia causes aperistalsis and incomplete LES relaxation. Distal esophageal spasm causes simultaneous contractions with a normal LES. Systemic sclerosis causes aperistalsis in the smooth muscle and a low LES pressure. Hypercontractile esophagus causes high-amplitude coordinated peristalsis.

Step-by-Step Solution

1
Analyze the lower esophageal sphincter (LES) resting pressure and relaxation parameters for each patient.
Incomplete relaxation suggests achalasia. Low resting pressure suggests systemic sclerosis. Normal relaxation limits the differential to distal esophageal spasm or hypercontractile esophagus.
LES function is the primary differentiator between hypertonic (achalasia) and hypotonic (scleroderma) disorders.
2
Evaluate the peristaltic pattern in the esophageal body to finalize the diagnosis.
Absent peristalsis is seen in achalasia and scleroderma. Premature, simultaneous contractions point to distal esophageal spasm. High-amplitude but coordinated contractions point to hypercontractile esophagus.
The combination of esophageal body peristaltic abnormalities and LES function definitively categorizes the specific esophageal motility disorder.

Key Concept

Diagnosis of esophageal motility disorders relies on evaluating both the contraction pattern of the esophageal body and the relaxation capacity of the lower esophageal sphincter on high-resolution manometry.
Question 1814Question →

Match the following clinical vignettes of central nervous system infections with their most appropriate targeted or empiric antimicrobial therapy.

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Items

A 72-year-old man presents with acute fever, nuchal rigidity, and confusion. Cerebrospinal fluid analysis reveals neutrophilic pleocytosis, elevated protein, and decreased glucose.
A 35-year-old man with a CD4 count of 45 cells/mm³ presents with a progressive headache. Cerebrospinal fluid cryptococcal antigen testing is positive.
A 45-year-old woman presents with fever, aphasia, and focal seizures. Magnetic resonance imaging of the brain demonstrates hyperintensity in the left temporal lobe.
A 28-year-old man with untreated HIV (CD4 count 30 cells/mm³) presents with left-sided hemiparesis. Brain imaging reveals multiple ring-enhancing lesions in the basal ganglia.

Matches

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Answer

Elderly meningitis matches with Ceftriaxone, Vancomycin, and Ampicillin; Cryptococcal meningitis matches with Amphotericin B and Flucytosine; HSV encephalitis matches with Intravenous acyclovir; Toxoplasma encephalitis matches with Sulfadiazine, pyrimethamine, and leucovorin.
Each clinical presentation directly corresponds to a specific infectious etiology that dictates its treatment. 1) Empiric therapy for bacterial meningitis in adults older than 50 years includes ceftriaxone (for pneumococcus and meningococcus), vancomycin (for resistant pneumococcus), and ampicillin (for Listeria). 2) Cryptococcal meningitis (positive CSF antigen) requires induction with amphotericin B and flucytosine. 3) HSV encephalitis (temporal lobe edema, focal neurologic signs) is treated with intravenous acyclovir. 4) Toxoplasma encephalitis (ring-enhancing lesions in advanced HIV) is treated with sulfadiazine, pyrimethamine, and leucovorin.

Step-by-Step Solution

1
Diagnose the underlying central nervous system infection based on the clinical vignette.
The vignettes describe bacterial meningitis in an elderly patient, cryptococcal meningitis in advanced HIV, HSV encephalitis, and Toxoplasma encephalitis in advanced HIV, respectively.
Accurate etiological diagnosis is necessary to select the appropriate empiric or targeted antimicrobial therapy.
2
Determine the guideline-concordant antimicrobial therapy for each identified condition.
Empiric meningitis therapy in patients over 50 years of age must include Listeria coverage (ampicillin). Cryptococcus requires amphotericin B and flucytosine. HSV requires acyclovir. Toxoplasmosis requires sulfadiazine and pyrimethamine.
Applying standard infectious disease guidelines optimizes patient outcomes and aligns with antimicrobial stewardship principles.

Key Concept

First-line antimicrobial therapy for common and opportunistic central nervous system infections
Estimated Time:1m 30s
Question 1815Question →

A 28-year-old man is referred to a gastroenterology genetics clinic for evaluation of early-onset colon polyps. A detailed family history reveals multiple relatives affected by various gastrointestinal and extraintestinal malignancies across several generations. Recognizing the specific extraintestinal manifestations is essential for identifying the underlying genetic disorder and initiating appropriate multisystem cancer screening. Match each hereditary gastrointestinal syndrome with its most characteristic extraintestinal manifestation or associated malignancy.

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Items

Peutz-Jeghers syndrome
Gardner syndrome
Turcot syndrome
Lynch syndrome

Matches

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Answer

Peutz-Jeghers matches with mucocutaneous pigmented macules; Gardner matches with osteomas and retinal hypertrophy; Turcot matches with central nervous system tumors; Lynch matches with endometrial, ovarian, and urothelial carcinomas.
Each hereditary gastrointestinal syndrome has a distinct phenotypic presentation due to specific genetic mutations. Recognizing these extraintestinal manifestations is critical for confirming the diagnosis and implementing targeted, life-saving cancer screening.

Step-by-Step Solution

1
Analyze the clinical scenario requirements.
The task requires correlating specific hereditary gastrointestinal syndromes with their classical extraintestinal manifestations.
Accurate syndrome identification dictates the appropriate multisystem screening protocols for the patient and their relatives.
2
Evaluate Peutz-Jeghers syndrome.
Matches with mucocutaneous pigmented macules on the lips, buccal mucosa, and digits.
This is the pathognomonic physical exam finding associated with STK11 gene mutations.
3
Evaluate Gardner syndrome.
Matches with osteomas, epidermoid cysts, and congenital hypertrophy of the retinal pigment epithelium.
These findings differentiate Gardner syndrome from classic familial adenomatous polyposis (FAP) despite sharing the same underlying APC gene mutation.
4
Evaluate Turcot syndrome.
Matches with malignant central nervous system tumors.
Turcot syndrome specifically defines the association between colonic polyposis and brain tumors, primarily medulloblastoma and glioblastoma.
5
Evaluate Lynch syndrome.
Matches with a high risk of endometrial, ovarian, and urothelial tract carcinomas.
Lynch syndrome involves mismatch repair gene mutations resulting in a wide array of extracolonic malignancies, with endometrial cancer being the most common.

Key Concept

Extraintestinal manifestations of hereditary gastrointestinal polyposis and nonpolyposis syndromes
Question 1816Question →

A 65-year-old hospitalized patient is evaluated for acute-onset hypotension and signs of poor organ perfusion. The intensive care team places a pulmonary artery (Swan-Ganz) catheter to determine the specific etiology of the shock state. Match each set of central hemodynamic parameters obtained from the catheterization to the most likely underlying clinical condition.

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Items

RAP: 16 mm Hg (↑), PCWP: 20 mm Hg (↑), CI: 1.6 L/min/m² (↓), SVR: 2200 dynes/sec/cm⁻⁵ (↑)
RAP: 2 mm Hg (↓), PCWP: 4 mm Hg (↓), CI: 1.8 L/min/m² (↓), SVR: 2400 dynes/sec/cm⁻⁵ (↑)
RAP: 18 mm Hg (↑), PAP: 60/25 mm Hg (↑), PCWP: 8 mm Hg (↔), CI: 1.7 L/min/m² (↓)
RAP: 4 mm Hg (↔), PCWP: 6 mm Hg (↔), CI: 4.5 L/min/m² (↑), SVR: 500 dynes/sec/cm⁻⁵ (↓)

Matches

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Answer

The hemodynamic profiles match the four classic forms of shock: cardiogenic shock demonstrates high filling pressures and low output; hypovolemic shock demonstrates low filling pressures and low output; obstructive shock demonstrates high right-sided pressures with normal left-sided filling pressures; and distributive shock demonstrates low systemic vascular resistance with high output.
Right heart catheterization parameters are pivotal for differentiating shock etiologies. Cardiogenic shock presents as primary pump failure leading to backward transmission of volume (elevated RAP and PCWP) and low forward output (decreased CI). Hypovolemic shock originates from volume loss, resulting in critically low filling pressures (decreased RAP and PCWP) and low output. Obstructive shock from a pulmonary embolism acutely blocks the right heart outflow tract, leading to high right-sided pressures (elevated RAP and PAP) but leaves the left heart underfilled (normal PCWP). Finally, distributive shock is primarily a loss of systemic vascular tone (decreased SVR), leading to a compensatory hyperdynamic state with an elevated cardiac index.

Step-by-Step Solution

1
Evaluate Cardiac Index (CI) and Systemic Vascular Resistance (SVR).
Identifies hyperdynamic versus hypodynamic shock states.
Distributive shock is uniquely characterized by a high cardiac index and profoundly low systemic vascular resistance due to widespread vasodilation.
2
Examine Pulmonary Capillary Wedge Pressure (PCWP) in low-output states.
Differentiates cardiogenic shock from hypovolemic and obstructive etiologies.
An elevated PCWP indicates left-sided pump failure with volume backup, whereas a normal or low PCWP indicates an underfilled left heart.
3
Analyze Pulmonary Artery Pressure (PAP) and Right Atrial Pressure (RAP) in the setting of normal/low PCWP.
Identifies isolated right-sided obstructive pathophysiology.
Elevated right-sided pressures (RAP, PAP) combined with normal left-sided filling pressures (PCWP) indicate a barrier in the pulmonary circulation, such as a pulmonary embolism.

Key Concept

Hemodynamic Profiles of Shock
Question 1817Question →

For each immunocompromised patient described below, pair their clinical presentation with the most appropriate definitive targeted antimicrobial regimen for their suspected or confirmed opportunistic infection.

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Items

A patient with a CD4 count of 130 cells/mm³, progressive dyspnea on exertion, dry cough, and chest imaging showing bilateral ground-glass opacities.
A patient with a CD4 count of 60 cells/mm³, new-onset seizures, headache, and a brain MRI revealing multiple ring-enhancing lesions in the basal ganglia.
A patient with a CD4 count of 35 cells/mm³, persistent fevers, drenching night sweats, weight loss, and blood cultures growing acid-fast bacilli.
A patient with a CD4 count of 180 cells/mm³, severe retrosternal pain upon swallowing, and endoscopy revealing white, plaque-like lesions throughout the esophagus.

Matches

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Answer

The patient with bilateral ground-glass opacities (PCP) is matched with high-dose trimethoprim-sulfamethoxazole. The patient with multiple ring-enhancing lesions (Toxoplasmosis) is matched with pyrimethamine, sulfadiazine, and leucovorin. The patient with systemic symptoms and acid-fast bacilli (MAC) is matched with clarithromycin and ethambutol. The patient with odynophagia and esophageal plaques (Candida esophagitis) is matched with systemic fluconazole.
The correct pairings rely on pattern recognition of classic AIDS-defining illnesses. A CD4 count < 200 with interstitial pneumonia indicates PCP (requires TMP-SMX). A CD4 count < 100 with ring-enhancing brain lesions indicates Toxoplasmosis (requires pyrimethamine and sulfadiazine). A CD4 count < 50 with disseminated symptoms and acid-fast bacilli indicates MAC (requires clarithromycin and ethambutol). Odynophagia with white plaques indicates esophageal candidiasis (requires systemic fluconazole).

Step-by-Step Solution

1
Analyze the CD4 count and clinical syndrome for each patient to identify the specific opportunistic infection.
Identified the pathogens as Pneumocystis jirovecii, Toxoplasma gondii, Mycobacterium avium complex, and Candida albicans, respectively.
Different opportunistic infections predictably manifest when CD4 counts fall below specific thresholds (200, 100, and 50 cells/mm³), creating distinct clinical profiles.
2
Assign the guideline-recommended first-line pharmacotherapy for each identified active infection.
Paired PCP with TMP-SMX, Toxoplasmosis with pyrimethamine/sulfadiazine/leucovorin, MAC with clarithromycin/ethambutol, and Candida esophagitis with fluconazole.
Applying the correct targeted antimicrobial stewardship avoids treatment failure and minimizes inappropriate antibiotic exposure.

Key Concept

Diagnosis and targeted treatment of major HIV-associated opportunistic infections based on clinical presentation and CD4 cell count strata.
Estimated Time:1m 30s
Question 1818Question →

Match each clinical presentation and its associated physical examination findings with the most likely underlying structural or valvular cardiac pathology.

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Items

Exertional syncope; auscultation reveals a late-peaking systolic murmur at the right second intercostal space and delayed carotid upstrokes.
Worsening exertional dyspnea; auscultation reveals a blowing holosystolic murmur at the apex radiating to the axilla.
Wide pulse pressure and bounding pulses; auscultation reveals a high-pitched, early diastolic decrescendo murmur at the left sternal border.
Exertional chest pain; auscultation reveals a harsh systolic crescendo-decrescendo murmur at the left lower sternal border that becomes louder when moving from squatting to standing.
Hemoptysis and progressive dyspnea; auscultation reveals a loud S1, an opening snap, and a low-pitched mid-diastolic rumble at the apex.

Matches

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Answer

The correct matches directly link the location, timing, and dynamic characteristics of the murmurs to their corresponding valvular or structural lesions.
Each clinical scenario contains specific, pathognomonic physical examination findings that point directly to one cardiac abnormality. The pairings accurately reflect these classic associations as routinely tested on the USMLE Step 2 CK exam.

Step-by-Step Solution

1
Analyze the location and timing of the murmur described in each clinical presentation.
Identified systolic murmurs (aortic stenosis, mitral regurgitation, hypertrophic cardiomyopathy) and diastolic murmurs (aortic regurgitation, mitral stenosis).
Timing and location are the primary ways to differentiate heart murmurs.
2
Correlate dynamic auscultation changes or associated peripheral findings.
Distinguished the murmur of hypertrophic cardiomyopathy (increases with standing) from aortic stenosis (presents with delayed carotid upstrokes).
Maneuvers and pulse characteristics provide definitive diagnostic clues for morphologically similar murmurs.
3
Match the complete clinical and auscultatory profiles with the correct etiologies.
All five presentations correctly paired with their structural abnormalities.
Synthesizing the physical exam findings leads directly to the underlying cardiac pathology.

Key Concept

Clinical presentation and auscultatory findings of valvular heart diseases and structural cardiomyopathies
Estimated Time:1m 30s
Question 1819Question →

Match each patient's clinical presentation and dynamic auscultation findings to the most likely underlying structural or valvular pathology.

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Items

A 22-year-old athlete presents with a harsh crescendo-decrescendo systolic murmur at the left lower sternal border that increases in intensity when transitioning from squatting to a standing position.
A 75-year-old man presents with a harsh crescendo-decrescendo systolic murmur at the right upper sternal border. The murmur decreases in intensity during the strain phase of the Valsalva maneuver.
A 45-year-old woman presents with a late systolic murmur preceded by a mid-systolic click at the apex. The click occurs earlier in systole when she stands up from a sitting position.
A 60-year-old man presents with a high-pitched, blowing, early diastolic decrescendo murmur at the left sternal border that becomes louder with sustained isometric handgrip.
A 65-year-old woman with a history of myocardial infarction presents with a blowing holosystolic murmur at the apex that radiates to the axilla and becomes louder with sustained isometric handgrip.

Matches

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Answer

The presentations map as follows: the athlete with a louder murmur on standing has hypertrophic cardiomyopathy; the older man with a softer murmur on Valsalva has calcific aortic stenosis; the woman with an earlier click on standing has mitral valve prolapse; the man with a louder diastolic murmur on handgrip has aortic regurgitation; and the woman with a louder holosystolic murmur on handgrip has mitral regurgitation.
Each pairing correctly applies the principles of dynamic auscultation. Maneuvers that decrease preload (Valsalva strain, standing) soften most murmurs due to reduced transvalvular flow. The notable exceptions are hypertrophic cardiomyopathy (murmur becomes louder due to increased obstruction) and mitral valve prolapse (click occurs earlier and murmur lengthens). Maneuvers that increase afterload (handgrip) increase regurgitant murmurs like AR and MR by raising the pressure gradient driving backward flow, but decrease forward-flow murmurs like AS and HCM.

Step-by-Step Solution

1
Identify the baseline murmur characteristics (timing, quality, location).
Categorized murmurs into systolic (HCM, AS, MVP, MR) and diastolic (AR).
Baseline characteristics severely limit the differential diagnosis.
2
Determine the hemodynamic effect of the described physical maneuvers.
Standing and Valsalva decrease preload. Handgrip increases afterload.
Dynamic maneuvers manipulate blood volume and pressure gradients to distinguish similar-sounding murmurs.
3
Apply the hemodynamic change to the specific valvular or structural defect.
Decreased preload intensifies HCM and MVP murmurs but softens AS. Increased afterload intensifies regurgitant murmurs (AR, MR).
This confirms the specific pathophysiological mechanism underlying each presentation.

Key Concept

Dynamic auscultation and structural heart disease
Question 1820Question →

Match each clinical presentation and thyroid laboratory profile with its most accurate underlying pathophysiologic mechanism.

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Items

A 28-year-old woman with weight loss and tachycardia. Labs: TSH <0.01<0.01 μ\mu U/mL, elevated free T4, and a diffuse radioactive iodine uptake of 65%65\% (normal 8−25%8-25\%).
A 35-year-old woman with fever and severe anterior neck pain. Labs: TSH <0.01<0.01 μ\mu U/mL, elevated free T4, radioactive iodine uptake of <1%<1\%, and markedly elevated serum thyroglobulin.
A 42-year-old medical worker with anxiety and a nonpalpable thyroid. Labs: TSH <0.01<0.01 μ\mu U/mL, elevated free T4, radioactive iodine uptake of <1%<1\%, and undetectable serum thyroglobulin.
A 45-year-old man with palpitations and bitemporal hemianopsia. Labs: TSH 6.56.5 μ\mu U/mL (normal 0.4−4.00.4-4.0 μ\mu U/mL), elevated free T4, and elevated serum alpha-subunit levels.

Matches

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Answer

The correct matches map the varying combinations of TSH, free T4, radioactive iodine uptake, and thyroglobulin to their distinct thyrotoxic etiologies (Graves disease, subacute thyroiditis, exogenous thyroid hormone, and a TSH-secreting pituitary adenoma).
Evaluating thyrotoxicosis requires a stepwise approach. An inappropriately elevated TSH with high free T4 indicates a central cause, most commonly a TSH-secreting pituitary adenoma (further supported by high alpha-subunits and compressive mass effects like bitemporal hemianopsia). In primary hyperthyroidism (suppressed TSH), a high radioactive iodine uptake (RAIU) signifies overproduction of hormone, such as in Graves disease caused by TSH-receptor autoantibodies. If RAIU is low, the hyperthyroidism is either from follicular destruction (subacute thyroiditis) or exogenous hormone use. Serum thyroglobulin successfully differentiates these two: it is elevated during follicular destruction but suppressed by exogenous hormone administration.

Step-by-Step Solution

1
Evaluate TSH and free T4 levels to establish the level of the defect.
Three patients have primary hyperthyroidism (low TSH, high free T4), while one has central hyperthyroidism (high TSH, high free T4).
This immediately isolates the central hyperthyroidism case (TSH-secreting adenoma).
2
Analyze the radioactive iodine uptake (RAIU) for the primary hyperthyroidism cases.
One patient has high/diffuse uptake (Graves disease), while two have severely decreased uptake.
High RAIU indicates de novo hormone production. Low RAIU indicates either release of preformed hormone or an exogenous hormone source.
3
Use serum thyroglobulin to distinguish the remaining two cases of primary hyperthyroidism with low RAIU.
The patient with elevated thyroglobulin and a tender neck has subacute thyroiditis. The patient with undetectable thyroglobulin has exogenous hormone ingestion.
Thyroglobulin is co-secreted during endogenous thyroid hormone release but is completely suppressed when exogenous hormone causes thyrotoxicosis.

Key Concept

The diagnostic workup of thyrotoxicosis relies on TSH and free T4 to identify the primary vs. central source, followed by radioactive iodine uptake and thyroglobulin to differentiate mechanisms of primary hyperthyroidism.
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