Rheumatological mimic: primary hypertrophic osteoarthropathy initially treated as juvenile idiopathic arthritis

Primary hypertrophic osteoarthropathy (PHO) is a rare genetic disorder that closely mimics inflammatory arthritis, leading to diagnostic delays and inappropriate treatment. We report the case of an adolescent boy who presented with a 2-year history of intermittent joint pain and swelling and was initially diagnosed with juvenile idiopathic arthritis at a primary care centre. He was treated with sulfasalazine but experienced only partial symptomatic relief. Laboratory evaluation at the referring centre showed a negative rheumatoid factor and mildly elevated C-reactive protein. Persistent symptoms prompted re-evaluation, which revealed clinical features and a positive family history consistent with PHO. Recognition of characteristic clinical findings and family history led to the correct diagnosis, allowing discontinuation of the disease-modifying anti-rheumatic therapy. This case highlights the importance of considering PHO in the differential diagnosis of chronic arthritis in children, particularly in those with a positive family history.