Collagen type V polymorphism in spontaneous quadriceps tendon ruptures.

Spontaneous simultaneous bilateral quadriceps tendon rupture is associated with multiple medical conditions and pharmacological treatments; however, identifying prior risk factors is impossible in most cases. Achilles tendon and anterior cruciate ligament ruptures are associated with collagen, type V, alpha 1 (COL5A1) polymorphism. This genetic variant may be implicated quadriceps tendon rupture. The COL5A1 encodes the protein for pro-α1 chains of the low-abundance heterotrimeric type V collagen. In most noncartilaginous tissues, type V collagen is a quantitatively minor component of type I collagen that has been implicated in the regulation of the size and configuration of type I collagen fibrils. The functional significance of COL5A1 polymorphism in relation to type V collagen expression or activity has not been determined.This article describes a patient with COL5A1 polymorphism and spontaneous simultaneous quadriceps tendon rupture. However, genetic and histologic studies performed on blood and tendon tissues and 3 consecutive sex- and age-matched controls showed a statistically significant reduction in collagen type V expression and an alteration in collagen structure in the tendon. These findings might explain the pathomechanisms of spontaneous tendon ruptures associated with COL5A1 polymorphism.