Psoriatic arthritis can mimic which autoimmune disease?

• A. Rheumatoid Arthritis
• B. Systemic Lupus Erythematosus
• C. Sjögren's Syndrome
• D. Ankylosing Spondylitis

Answer: (A)

Psoriatic arthritis can resemble rheumatoid arthritis because both are autoimmune inflammatory arthritides that often present with inflammatory polyarthritis—joint swelling, morning stiffness, and pain in the small joints of the hands. This overlap is why rheumatoid arthritis is the best answer: it is the prototypical inflammatory arthritis, and PsA frequently mimics it, especially early on when psoriasis skin findings may be subtle or not yet recognized.

Clinically, you might see PsA with a similar symmetric pattern, but there are clues that point toward PsA: involvement of the distal interphalangeal joints, dactylitis (swelling of an entire finger or toe), enthesitis (tendon/ligament insertion sites, like the Achilles), and sometimes an asymmetric or oligoarticular distribution. Serology can help too—RA often has positive rheumatoid factor or anti-CCP antibodies, though not always, whereas PsA is frequently seronegative. Radiographs can also differ, with PsA showing erosions that may be accompanied by new bone formation, whereas RA tends to have erosions and joint-space narrowing without the same pattern of new bone formation early on.

So, the best fit is rheumatoid arthritis because PsA most commonly mimics that pattern of inflammatory, small-joint arthritis.