[Intraoperative diagnosis of alkaptonuria during lumbar disc surgery: A case report].

A 56-year-old man presented with low back pain radiating to the left leg.CT of the lumbar spine revealed reduced disc height and a vacuum phenomenon. MRI demonstrated a left-sided disc herniation at L3-L4, considered the cause of symptoms. Intraoperatively, however, the disc material appeared unusually dark and pigmented.Histological analysis confirmed ochronotic pigment deposits, leading to the diagnosis of alkaptonuria (AKU).The surgical procedure was completed as planned. Postoperatively, the patient was referred for further internal medicine evaluation and genetic counselling.When encountering atypically pigmented tissue, surgeons should consider rare metabolic disorders such as AKU, allowing early diagnosis and appropriate long-term management.