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Psoriatic arthritis — USMLE Step 3 MCQ

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ModerateAmbulatory Medicine / Primary CarePsoriatic arthritisUSMLE Step 3

A 50-year-old man with chronic plaque psoriasis has persistent joint pain and morning stiffness in the distal interphalangeal joints. Examination shows nail pitting and dactylitis of one toe. Rheumatoid factor is negative. Which of the following is the most likely diagnosis?

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Correct answer: A — Psoriatic arthritis

Psoriasis with inflammatory joint symptoms, nail pitting, distal interphalangeal involvement, and dactylitis is characteristic of psoriatic arthritis.

Reference: American College of Rheumatology/National Psoriasis Foundation psoriatic arthritis guidance