Alkaptonuria, a rare cause of early arthrosis in weight bearing joints – case report and review of literature

Abstract

Alkaptonuria is a rare autosomal recessive disorder caused by deficiency in homogentisate 1,2-dioxygenase, which leads to a tissue accumulation of homogentisic acid (HGA). HGA irreversibly deposits in connective tissues, which leads to degeneration of the articular cartilage, leaving these tissues with dark pigmentation, known as ochronosis. Alkaptonuria typically presents with a triad of homogentisic aciduria, ochronosis and ochronotic arthropathy during the third and fourth decade of life. The ochronotic arthropathy is the most impactful complication in the quality of life, even though it virtually impacts every system. There is no effective treatment, so intervention is based on symptoms, maintaining function and pain control while the inevitable deterioration of weightbearing joints progresses. Almost all patients are submitted to arthroplasties of the knee and/or hip. Soon there might be a way to prevent complications, has there are ongoing phase 3 studies to approve a drug that blocks the formation of HGA.