“Monarthritis” in a young man

A 20 year old male university student presented with a one year history of a stiff painful swollen left ankle. He described morning stiffness of one hour and also night pain which occasionally kept him awake. He was unable to take part in sporting activities. There was no history of trauma. No other joints were painful. There was no history of back or heel pain, psoriasis, iritis, urethritis, or inflammatory bowel disease. There was no history of preceding gastrointestinal or genitourinary infection. He had had an episode of Stevens-Johnson syndrome at the age of 12 (but no recent skin or mouth lesions) and occasional migraine headaches. His health was otherwise good. There was no history of weight loss. Non-steroidal anti-inflammatory drugs provided more symptomatic relief than simple analgesics. His grandmother had rheumatoid arthritis. There was no other significant family history. Clinical examination demonstrated a large warm ankle effusion with generalised tenderness, stress pain, and significantly decreased ankle movement. No abnormality was found on examination of the remainder of the locomotor system. There was no evidence of psoriasis or other rash or nail lesion. The remainder of the clinical examination was …