A 62-year-old man presents to the clinic with a 3-month history of progressive muscle weak… — USMLE Step 2 CK

A $62$ -year-old man presents to the clinic with a $3$ -month history of progressive muscle weakness and fatigue. He reports increasing difficulty getting up from a seated position, climbing stairs, and brushing his hair. Over the past month, he has also noticed a mildly pruritic, violaceous eruption on his upper eyelids and an erythematous, scaly rash over the dorsal aspects of his metacarpophalangeal and interphalangeal joints. His medical history includes hypertension and hyperlipidemia, for which he has taken lisinopril and atorvastatin for the past $5$ years. Vital signs are within normal limits. Neurologic examination demonstrates $4/5$ motor strength in the bilateral deltoid, hip flexor, and quadriceps muscles, with normal distal strength. Sensation and deep tendon reflexes are intact. Laboratory evaluation reveals a serum creatine kinase level of $2,400 \text{ U/L}$ and an aldolase level of $15 \text{ U/L}$ (normal: $1.0 - 7.5 \text{ U/L}$ ). A screening thyroid-stimulating hormone (TSH) level is $2.5 \text{ \mu U/mL}$ (normal: $0.4 - 4.0 \text{ \mu U/mL}$ ). Based on the most likely diagnosis, which of the following is the most appropriate additional evaluation for this patient?

Age-appropriate malignancy screeningCevap
B
Measurement of free thyroxine (T4) levels
C
Evaluation of arterial blood gas
D
Echocardiography to assess for pulmonary hypertension
E
Blood cultures and cutaneous punch biopsy for bacterial culture

Cevap

The most appropriate next step is to perform age-appropriate malignancy screening, as the patient has classic signs of dermatomyositis, which is often a paraneoplastic syndrome in older adults.

The correct answer identifies the need for malignancy screening. The patient's presentation of symmetric proximal muscle weakness, elevated muscle enzymes (creatine kinase, aldolase), and pathognomonic cutaneous findings (heliotrope rash on eyelids, Gottron papules on knuckles) is classic for dermatomyositis. Up to

15\%

25\%

of adult patients with dermatomyositis have an underlying malignancy, most commonly adenocarcinomas of the cervix, lung, pancreas, breast, ovaries, or gastrointestinal tract. Because dermatomyositis often presents as a paraneoplastic syndrome in older adults, comprehensive age-appropriate malignancy screening (e.g., colonoscopy, chest radiography or CT, age-appropriate cancer markers) is a critical next step in evaluation once the diagnosis is suspected or established.

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Analyze the patient's clinical presentation and physical examination findings.

The patient exhibits symmetric proximal muscle weakness and pathognomonic cutaneous signs: a heliotrope rash (violaceous periorbital eruption) and Gottron papules (scaly rash on the knuckles).

Identifying these classic signs establishes the clinical diagnosis of dermatomyositis.

Evaluate the laboratory results to rule out other causes of myopathy.

The highly elevated creatine kinase and aldolase confirm muscle breakdown. The normal TSH effectively rules out hypothyroid myopathy.

Excluding endocrine and metabolic etiologies confirms the autoimmune inflammatory nature of the disease.

Identify the most critical clinical associations for the established diagnosis.

Adult-onset dermatomyositis is strongly associated with underlying occult malignancies in up to 15-25% of cases.

Recognizing dermatomyositis as a potential paraneoplastic syndrome dictates the immediate next steps in patient evaluation.

Select the most appropriate evaluation based on the disease association.

Age-appropriate malignancy screening is the mandatory next step.

Early detection of an associated malignancy is crucial for modifying patient survival and managing the underlying trigger of the paraneoplastic autoimmune response.

Anahtar Kavram

Adult-onset dermatomyositis is strongly associated with occult malignancies, and patients require prompt age-appropriate malignancy screening upon diagnosis.

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