Alkaptonuria Presenting With Lumbar Disc Herniation: A Case Report

Alkaptonuria is a rare autosomal recessive trait. Symptomatic lumbar disc herniation warranting surgical intervention is a rare scenario in alkaptonuria and only a few cases have been described in the literature. We present one such rare case of alkaptonuria in a 31-year-old female presenting with low back pain and left leg radiculopathy not relieved with conservative management. Roentgenograms of the lumbar spine revealed wafer-like disc calcifications and MRI showed a herniated disc at the L4-L5 level with deeply hypointense disc spaces in T2 suggestive of disc calcification and associated modic type 2 changes. During the surgery, the disc material removed was black in color, which raised a clinical suspicion of alkaptonuria. Postoperatively, the patient was re-examined and urine homogentisic acid was found to be raised. This, along with a histopathological examination, was diagnostic of alkaptonuria. The patient had excellent relief of symptoms postoperatively. In conclusion, if a 'black disc' is found during surgery, retrospective analysis and re-examination of patient clinical features and urine examination have to be done to diagnose alkaptonuria. While making a differential diagnosis of degenerative disc disease in patients with a calcified disc seen on radiography, a high index of suspicion for alkaptonuria has to be maintained.