Black-Colored Ligamentum Flavum Due to Alkaptonuria

Abstract

Alkaptonuria is a rare metabolic disease caused by deficiency of homogentisic acid oxidase and characterized by bluish-black discoloration of cartilages and skin (ochronosis). Defective production of this enzyme results in the accumulation of homogentisic acid (HGA), a tyrosine degradation product, in the bloodstream. Accumulation of HGA and its metabolites in tissues causes ochronosis. The word ochronosis refers to the dark bluish-black discoloration of connective tissues including the sclera, cornea, auricular cartilage, heart valves, articular cartilage, tendons, and ligaments. Neurogenic claudication resulting from focal hypertrophy of the ligamentum flavum in the lumbar spine due to ochronotic deposits has only been previously reported once in the literature. In this article, we present a 71-year-old male patient with alkaptonuria-associated degenerative L3–L4–L5 stenosis, diagnosed after lumbar decompressive laminectomy.

Neglected Alkaptonuric Patients Presented with Symptomatic Degenerative Disc Disorders: Report of Two Cases and Review of Literature

“…AKU diagnosis is established based on ochronosis of tissues, ligaments, facet joints, black-colored discs, and black discoloration of urine after alkalization [10]. Retrospective examination of patients usually reveals signs of ochronotic deposits in tissues including ear, nose and sclera [10]. Likewise, after observation of extracted black intervertebral disc and re-examination of our patient (Case 1), we found nasal and ear discoloration as well as positive urine analysis.…”

“…AKU diagnosis is established based on ochronosis of tissues, ligaments, facet joints, black-colored discs, and black discoloration of urine after alkalization [10]. Retrospective examination of patients usually reveals signs of ochronotic deposits in tissues including ear, nose and sclera [10].…”