Review Question - QID 106426

The radiograph of both hands demonstrates pencil-in-cup deformities of both thumbs and erosion of the DIP joint of left middle finger, making psoriatic arthritis (in the context of the scaly rashes on the bilateral elbows) the most likely diagnosis.

Psoriatic arthritis is an inflammatory arthritis associated with psoriasis. Although it most commonly presents in patients who already have documented psoriasis, up to 20% of patients develop arthritis before the development of psoriatic skin lesions. The characteristic findings in psoriatic arthritis include distal interphalangeal (DIP) joint involvement (often with osteolysis resulting in the classic pencil-in-cup deformity), asymmetry, dactylitis (known commonly as "sausage digits"), flail or ankylotic deformities of the digits, and the frequent presence of enthesitis and spinal involvement.

Weigle et al. review psoriasis and its associated with systemic manifestations. They write that psoriasis is associated with several non-skin disorders including arthritis, cardiovascular disease, lymphoma, and depression.

Reveille et al. discuss the extensive clinical overlap between psoriatic arthritis, psoriasis, and Reiter's syndrome. Based on the results of their study, they hypothesized that some forms of psoriatic arthritis (e.g. HIV-associated) may constitute a spondlyarthropathy more closely related to reactive arthritis (also known as, Reiter's syndrome).

Figure A shows the characteristic findings of psoriatic arthritis on radiographs (pencil-in-cup deformities of both thumbs and erosion of the DIP joint of left middle finger).

Incorrect Answers:
Answer 1: Gouty arthritis is usually a monoarticular arthritis and does not show pencil-in-cup deformities.
Answer 2: Osteoarthritis is associated with morning stiffness that lasts less than an hour; it is also associated with different findings on imaging (e.g. joint space narrowing, osteophytes, and subchondral sclerosis).
Answer 3: RA does not affect the DIP joints and does not show cup-and-pencil deformities on imaging. Also, RA frequently presents with other constitutional symptoms.
Answer 5: Arthritis associated with systemic lupus erythematosus is generally associated with other constitutional symptoms.