An unusual cause of chronic backache.

A 46-year-old man of mixed race had been followed up for the past 7 years at our Rheumatology clinic. He was labelled as ‘burnt out’ rheumatoid arthritis with secondary osteoarthritis. Methotrexate had been stopped 5 years ago. His main complaint was chronic lower backache that had been worsening over the past few years. He did not have any symptoms suggestive of an inflammatory arthropathy. His grandfather had similar symptoms. His siblings were all healthy. Examination revealed a middle-aged male of short stature (1.51m). Back examination revealed loss of lumbar lordosis, limited extension with fairly preserved forward and lateral flexion. There was no evidence of peripheral arthritis and systemic examination was unremarkable. Radiographs of his lumbar spine revealed scoliosis, degenerative changes (marginal osteophytes, loss of joint space) and striking calcification of the intervertebral discs (Figure 1). Early degenerative changes of both radio carpal joints and metatarsophalangeal joints were also noted. No peripheral joint space calcification or any changes suggestive of an inflammatory arthropathy were noted. Laboratory investigation revealed normal renal function, ferritin and serum calcium. A urine sample showed high levels of homogentisic acid (HGA). Tyrosine and phenylalanine metabolites were not detected in the urine. The presence of intervertebral disc calcification and high urine HGA levels prompted the diagnosis of alkaptonuria (ochronosis). Discussion