Hurler Syndrome (MPSI H)

Among the cells in which mucopolysaccharides accumulate in Hurler syndrome are endothelial cells. In this photo one sees glistening and thickened endocardium in the left atrium and ventricle and on the mitral valve.

Marked thickening with some nodularity is seen in the septal and anterior leaflets of the tricuspid valve. In some cases mucopolysaccharides also accumulate subendothelially in coronary arteries leading to myocardial ischemia.

The mucopolysaccharidoses (MPS) result from deficiencies of lysosomal enzymes related to the degradation of mucopolysaccharides which are long-chain carbohydrates linked with proteins to form proteoglycans which are constituents of the ground substance of connective tissue. The deficiencies are determined on a genetic basis. Hurler syndrome (MPS I H), one of the most severe forms of MPS, is due to a deficiency of alpha-1-iduronidase. Normal at birth, affected infants or children develop hepatosplenomegaly, growth retardation, coarse facial features, and skeletal deformities. They usually die within the first decade of life and death is often secondary to cardiac involvement.

Contributed by Dr. Don B. Singer