Alkaptunuria; a case report

INTRODUCTION AND IMPORTANCE: Alkaptonuria is an autosomal recessive disease due to lack of the enzyme homogentisic acid oxidase. Homogentisic Acid (HA) is in the metabolism pathway of phenylalanine. The musculoskeletal symptomatology begins generally in the fourth decade. We reported the case of a 50 year old man who had ochronotic arthropathy and degenerative changes in knee joint and who was treated with total knee arthroplasty. CASE PRESENTATION: A 50 year old man presented to our outpatient clinic with bilateral knee pain. Pain was exaggerated with effort and decreases with rest. The patient had no medical history. While performing the total knee arhtroplasty for our patient, we discovered intraoperatively the black coloration of the articular cartilage of the knee. At 6 months follow up, the patient was satisfied with the result with no knee pain in the treated knee. Range of knee motion was 0° in total extension to 100° of flexion. Radiological control showed a stable prosthesis not affected by ochronose. CLINICAL DISCUSSION: Alkaptonuria is caused by lack of the enzyme homogentisic acid oxidase, is a rare autosomal recessive disease leading accumulation of homogentisic acid in connective tissue. This leads to many manifestations such as urinary, cardiac, dermatologic, ophthalmologic or musculoskeletal symptoms. Deposit of Homogentisic acid in articular cartilage gives the characteristic black or dark brown pigmentation of the cartilage. Its clinical traduction is symptomatology of degenerative modifications in multiples joints such as knee, shoulder or hip beside the lumbar spine arthrosis. CONCLUSION: Alkapyonuria is a very rare condition. Revealed by its orthopedic features is exceptionally. The patients, generally, need articulations replacement and the illness have no effect on its prognosis.