What clinical features should I assess to differentiate psoriatic arthritis from other types of inflammatory arthritis?

To differentiate psoriatic arthritis (PsA) from other types of inflammatory arthritis, assess the following clinical features:

• Presence of psoriasis: Current or past psoriasis is a key indicator, as PsA commonly occurs in people with psoriasis or a family history of psoriasis ³.
• Dactylitis (sausage digits): This is a strong clinical sign with a high likelihood ratio for PsA and spondyloarthritis, and its presence alone justifies referral for specialist assessment ¹,³.
• Enthesitis: Inflammation at tendon or ligament insertion sites is common in PsA but should be considered alongside other features, as enthesitis alone has weak predictive value ¹,³.
• Peripheral arthritis pattern: PsA often presents with peripheral joint involvement that can be asymmetric and may affect distal interphalangeal joints, unlike rheumatoid arthritis which is typically symmetric ¹,³.
• Extra-articular manifestations: Look for associated features such as nail changes (pitting, onycholysis), uveitis, and inflammatory bowel disease, which support a diagnosis of PsA or related spondyloarthritis ¹,³.
• Response to NSAIDs: Improvement of symptoms within 48 hours of NSAID use supports inflammatory arthritis but is not specific to PsA ³.
• Family history: A first-degree relative with psoriasis or spondyloarthritis increases the likelihood of PsA ³.

Referral to rheumatology is recommended if PsA is suspected, especially with dactylitis or persistent enthesitis, to confirm diagnosis and initiate early treatment to prevent joint damage ¹,⁴.