INTRODUCTION Fabry disease is an X-linked error of glycosphingolipid catabolism caused by the deficient activity of the lysosomal hydrolase α-galactosidase A (α-gal A) in tissues and fluids of affected hemizygous males; most heterozygous females have an intermediate level of enzymatic activity. The enzymatic defect leads to a systemic deposition of glycosphingolipids, predominantly globotriaosylceramide (Gb3), in body fluids and in the lysosomes of endothelial, perithelial, and smooth-muscle cells of blood vessels. Deposition also occurs in ganglion cells.