Intracellular collagen fibrils in cardiac valves of patients with the Hurler syndrome.

Ultrastructural study of thickened mitral and tricuspid valves from three patients with the Hurler syndrome disclosed collagen fibrils located within membrane-bound cytoplasmic dense bodies in small granular cells. These cells, which differ morphologically from the clear cells containing mucopolysaccharide deposits, are considered to be fibroblasts in advanced stages of degeneration. It is postulated that the elevated concentrations of dermatan sulfate in Hurler's disease lead to an abnormally high synthesis of collagen and to its polymerization in intracellular loci.