Bilateral spontaneous rupture of the quadriceps tendon as an initial presentation of alkaptonuria--a case report.

Unilateral rupture of the quadriceps tendon is not uncommon, but bilateral spontaneous quadriceps tendon rupture is a rare occurrence and is usually associated with some underlying predisposing condition. We describe a case of a previously healthy patient who presents with bilateral spontaneous rupture of both quadriceps tendon. Investigations revealed that he had underlying alkaptonuria which was previously undiagnosed. Alkaptonuria is a rare inborn metabolic disease, which results in the derangement of homogentisic acid metabolism. Excessive accumulation of homogentisic acid is known to affect multiple organ systems, resulting in tendinopathy and arthropathy in the muscoskeletal system.