Back pain and fever: when the diagnosis becomes crystal clear

In April 2015, a 61-year-old man presented to a tertiary hospital in Melbourne, Australia, with generalised weakness and left knee pain. He had a past history of type-2 diabetes and gout. Clinical examination revealed a warm, tender left knee with effusion. Laboratory findings included an elevated serum uric acid 679 μmol/L (normal 180–420 μmol/L), C-reactive protein (CRP) 215 mg/L (normal 0–5 mg/L) and creatinine 138 μmol/L (normal 66–105 μmol/L). Joint aspirate of the left knee revealed monosodium urate crystals. Prednisolone (50 mg/daily) resulted in symptomatic and biochemical improvement. Allopurinol (50 mg/daily) was introduced on day 17 while prednisolone was tapered. Over the following fortnight, he developed worsening thoracolumbar back pain associated with episodic pyrexia and hypotension. Pertinent laboratory findings included CRP up to 329 mg/L. Serology and cultures of blood, urine and