A 25 year old Bengali woman presented acutely with a symmetrical inflammatory polyarthritis affecting knees, wrists, metacarpophalangeal (MCP) joints, and proximal interphalangeal (PIP) joints which had developed over six weeks. The distal interphalangeal joints were spared. She had a pigmented, scaly rash over the hands, chest, and back. There had been no fever, hair loss, mouth ulcers, genitourinary symptoms, Raynaud's phenomenon, and no significant past medical history. At presentation there was no lymphadenopathy or organomegaly. Initial investigations showed (normal range): haemoglobin 106 g/l (135–180 g/l), mean corpuscular volume 72.7 fl (76–96 fl), white cell count (WCC) 18 × 10⁹/l (neutrophilia) (4–11 × 10⁹/l), platelets 301 × 10⁹/l (150–400 × 10⁹/l), urea 6.2 mmol/l (3.0–8.3 mmol/l), creatinine 50 μmol/l (44–133 μmol/l), alanine aminotransferase 71 IU (<50 IU), alkaline phosphatase 361 IU/l (20–130 IU), albumin 40 g/l (35–50 g/l), ferritin 1200 μg/l (10–300 μg/l), plasma viscosity 2.1 mPa.s (1.50–1.72 mPa.s), C reactive protein (CRP) 230 mg/l (<5 mg/l), C3 and C4 levels normal, antinuclear antibodies (ANA), antineutrophil cytoplasmic antibodies (ANCA), and rheumatoid factor were negative. Blood cultures, hepatitis B and C serology, and the monospot test for glandular fever were negative. Radiographs of the hands showed soft tissue swelling around MCP and PIP joints, but were otherwise normal. A chest radiograph was normal. A differential diagnosis of seronegative rheumatoid arthritis and adult onset Still's disease (AOSD) was considered. Oral methotrexate 7.5 mg weekly, prednisolone 15 mg daily, and diclofenac 50 mg three times …