[Alkaptonuria and ochronotic arthropathy. Arthroscopic and intraoperative findings in implantation of a knee joint surface replacing prosthesis].

Alcaptonuria is a rare (incidence approx. 1:10(6)), autosomal-recessive transmitted metabolic disease. The basic defect is a lack of the enzyme homogentisic acid oxidase. During metabolism of phenylalanin and tyrosin to fumaric acid and acetoacetic acid this enzymatic defect causes an accumulation of the intermediate breakdown product homogentisic acid in bradytrophic tissues resulting in pigmentation and calcification of the intervertebral disks. We present a 57 year old female patient in whom we diagnosed alcaptonuria by the appearance of the typical symptom trias homogentisic acid excretion in the urine, ochronosis and arthritis. The anamnesis and results of a knee arthroscopy, radiographic and laboratory examinations as well as the intraoperative and histological findings during implantation of a knee joint surface replacing prosthesis (Gemini-System, Link Co., Hamburg, Germany) are reported.