Which diagnosis is most likely associated with patches of dry, erythematous skin on extensor surfaces and DIP joint enlargement?

Which diagnosis is most likely associated with patches of dry, erythematous skin on extensor surfaces and DIP joint enlargement?

• A. Reiter syndrome
• B. Psoriatic arthritis
• C. Rheumatoid arthritis
• D. Systemic lupus erythematosus

Answer: (B)

Patches of dry, erythematous skin on extensor surfaces together with distal interphalangeal (DIP) joint enlargement point to psoriasis with psoriatic arthritis. Psoriasis commonly affects extensor areas and nails, and when arthritis develops, the DIP joints are often involved, sometimes with new bone formation that can enlarge the joints. This pattern is distinct from rheumatoid arthritis, which typically presents with symmetric swelling of the small joints (MCP, PIP, wrists) rather than DIP enlargement. Reiter (reactive) arthritis can have mucocutaneous and plantar lesions but usually includes urethritis and conjunctivitis and does not center on DIP joint swelling with psoriasiform skin patches. Systemic lupus erythematosus shows varied skin rashes (like malar rash) and different joint patterns, not the combination described.

Patches of dry, erythematous skin on extensor surfaces together with distal interphalangeal (DIP) joint enlargement point to psoriasis with psoriatic arthritis. Psoriasis commonly affects extensor areas and nails, and when arthritis develops, the DIP joints are often involved, sometimes with new bone formation that can enlarge the joints. This pattern is distinct from rheumatoid arthritis, which typically presents with symmetric swelling of the small joints (MCP, PIP, wrists) rather than DIP enlargement. Reiter (reactive) arthritis can have mucocutaneous and plantar lesions but usually includes urethritis and conjunctivitis and does not center on DIP joint swelling with psoriasiform skin patches. Systemic lupus erythematosus shows varied skin rashes (like malar rash) and different joint patterns, not the combination described.