Distribution of α-Gal A activity and different GLA genotypes. (A) Distribution of α-Gal A activity and IVS4+919 G (wild type) or A (mutant) genotype. Note that the α-Gal A activity in the different genotypes of males and females overlapped. (B) Distribution of NAG/α-Gal A activity ratio and IVS4+919 genotypes. By use of this ratio cutoff, male patients, but not female herterozygotes, were more accurately detected. Male-G, males with IVS4+919G; Male-A, males with IVS4+919A; Female-GG, females with IVS4+919 GG; Female-AG, females with IVS4+919 AG; AGAL, α-Gal A.