A diagnostic trap in axial pain: Ochronotic spondylopathy masquerading as ankylosing spondylitis

Résumé fourni par la source

To the Editor, Alkaptonuria is a rare autosomal recessive disorder caused by homogentisate 1,2-dioxygenase deficiency, leading to systemic accumulation of homogentisic acid (HGA).Its hallmark, ochronosis, results from HGA polymer deposition in connective tissues, causing pathognomonic pigmentation and degenerative arthropathy.Because axial pain and stiffness often dominate the presentation, ochronotic spondylopathy frequently mimics ankylosing spondylitis (AS), leading to misdiagnosis and inappropriate immunomodulatory therapy.[1,2] We report a 47-year-old male who has had chronic axial pain since his mid-twenties.He had a four-year history of treatment for presumed AS with methotrexate, sulfasalazine, and nonsteroidal anti-inflammatory drugs, achieving only partial relief.The initial diagnosis was based on chronic inflammatory back pain and a positive human leukocyte antigen (HLA)-B27 test.On examination, bluish-grey discoloration were seen in both auricles (Figure 1).Spinal mobility was restricted and painful; chest expansion was 4 cm, and the modified Schober excursion was 3 cm.Laboratory testing showed elevated C-reactive protein (CRP), while erythrocyte sedimentation rate was within normal limits.Radiographs demonstrated multilevel intervertebral disc narrowing with prominent "wafer-like" calcifications and subchondral sclerosis.Contrast-enhanced sacroiliac magnetic resonance imaging performed as part of our assessment showed no evidence of sacroiliitis (Figure 2).A simple bedside observation strongly supported the diagnosis: the patient's urine darkened significantly after standing for 24 hours (Figure 3).

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