Alkaptonuria with rapidly destructive arthropathy of the hip: A case report and literature review.

Alkaptonuria-related rapidly destructive arthropathy of the hip joint has not been reported in detail with both imaging and histopathological findings in the literature. We, herein, presented the case of a 79-year-old male patient who suddenly started experiencing marked right hip pain. Radiography showed that the femoral head was spherical; however, after 3 months, approximately half of the femoral head was destroyed despite there being almost no change in the acetabulum. Radiographs of the spine also showed fusion between multiple vertebrae. Significant osteoporosis was observed on roentgenography, together with decreased bone density. Urinary gas chromatography-mass spectrometry analysis revealed that a large amount of homogentisic acid was excreted. During total hip arthroplasty, gray and muddy contents were observed in the joint capsule, and the surface of the destroyed femoral head was black. Histopathologically, granulomatous foci containing fragmented bone and cartilage debris were found in the bone marrow space of the joint surface, and the cartilage tissue was pigmented brownish black. The patient was subsequently diagnosed with ochronotic hip joint destruction. The present case report is the first to demonstrate rapidly destructive coxopathy associated with alkaptonuria using both imaging and histopathological findings. These findings clearly show that severe hip joint destruction defined as rapidly destructive hip arthropathy can occur in a very short time period for patients with alkaptonuria.