USMLE Rheumatology practice question

Question

A 50-year-old man complains of wrong term swelling and pain in his hands. This is worse in the morning and generally lasts about two hours. His father had psoriasis. Exam demonstrates tender and swollen MCP, PIP, wrist, and ankle joints.

Lab: CBC WNL except Hg 11 and Plt 400, ESR 46 CRP 21

Rheumatoid factor negative,Anti- CCP negative

ANA positive 1:80,Parvovirus IgM negative IgG positive

What is the most likely diagnosis?

A. Psoriatic arthritis

B. Rheumatoid arthritis

C. Lupus

D parvovirus

E. Reactive arthritis

Answer 1

B. Rheumatoid arthritis.

there are A few distractors here as common on USMLE. The key is the symmetric inflammatory small/medium joint arthritis that is worse in the morning. Father having psoriasis is irrelevant and red herring. Typical anemia of chronic disease which is mild and mild thrombocytosis associated with inflammation. Typically elevated inflammatory markers.Rheumatoid/Anti-CCP abs may be negative as in this case and it is called Seronegative rheumatoid arthritis. Arthritis common in parvovirus and can look just like rheumatoid arthritis and IgG may be positive even an acute infection but IgMwould be positive also. An ANA with titer 1/80 Not uncommon in healthy population and more common in rheumatoid arthritis. Aside from the arthritis (which can be like rheumatoid) no other findings of lupus and doesn’t meet criteria for classification