Pseudodeficiency of α-galactosidase A

Abstract

Apparent deficiency of .alpha.-galactosidase A was observed in a 51-yr-old, clinically healthy male, with no clinical symptoms of Fabry disease, and without excess urinary excretion of ceramide trihexoside. The deficiency, which was similar to that found in Fabry disease patients, could be demonstrated using both synthetic and natural substrates. This pseudodeficiency was transmitted in his family by classical X-linked inheritance. His wife showed enzyme activity in the normal range, 2 daughters were heterozygotes for this mutation as demonstrated by hair root assay, and 3 sons showed normal .alpha.-galactosidase activity. Kinetic studies in cultured skin fibroblasts indicated a 5-fold increase in the apparent Km and a greater heat stability of the residual .alpha.-galactosidase activity when compared to controls. The residual enzyme activity in this mutation seems to behave similarly to that observed in Fabry disease patients but does not cause any clinical abnormalities.