股関節痛からアルカプトン尿症の診断に至った1例

Severe Acute Coxalgia in Ochronotic Arthropathy. Case Report

　アルカプトン尿症はチロシン，フェニルアラニンの代謝経路での産物であるホモゲンチジン酸が組織に蓄積し黒色変色，退行変性を来す常染色体優性遺伝の代謝性疾患である．今回われわれはアルカプトン尿症性股関節症の症例を経験したので報告する．症例は特に既往歴のない69歳の女性で，軽微な外傷で股関節の急激な破壊を来し，人工股関節置換術を施行した．術中所見で骨頭，臼蓋軟骨の黒色変色を伴っており，術後にアルカプトン尿症との診断に至った．この症例を通して本疾患の特徴，病態，鑑別疾患などを文献的に考察し報告する．

　Ochronosis is a musculoskeletal manifestation of alkaptonuria, a rare hereditary metabolic disorder that is characterized by deficiency of homogentisate 1,2-dioxygenase activity in the liver and associated with various systemic abnormalities related to the deposition of homogentisic acid pigment.　We report the case of a 69-year-old woman who presented with rapidly progressive osteoarthritis of the hip.　Destruction of the joint and severe functional impairment necessitated total hip arthroplasty, and the outcome was satisfactory.　Intraoperatively, we observed black discoloration of the femoral head and the acetabulum.　Histological examination revealed brown ochronotic cartilage.　Darkening of the patient's urine was also observed.　The features of this disease and the differential diagnosis are discussed based on a review of the literature.