Which psoriatic arthritis subtype involves DIP joints?

• A. Spondylitis
• B. DIP arthritis
• C. RA-like polyarthritis
• D. Arthritis mutilans

Answer: (B)

In psoriatic arthritis, patterns of joint involvement help categorize the disease. Involvement of the distal interphalangeal joints (the joints at the tips of the fingers) is a recognized psoriatic arthritis pattern, often called DIP arthritis. This pattern stands out because it targets the joints closest to the nail bed and is frequently associated with nail psoriasis. It contrasts with other psoriatic patterns: spondylitis focuses on the spine and sacroiliac joints; a rheumatoid-arthritis–like polyarthritis mainly involves the MCP and PIP joints and resembles RA; and arthritis mutilans describes a severe, destructive form with telescoping of the digits. So DIP arthritis is the hallmark when the distal finger joints are predominantly affected in psoriatic arthritis.