[Contribution of genotyping in Fabry's disease]

Fabry's disease is an X-linked disorder due to mutations in the GLA gene encoding the lysosomal enzyme alpha-galactosidase A. Clinically, most patients present with the "classical" form, though "variant" forms with inaugural or preminent heart or kidney involvement have been described. Heterozygous women are most often symptomatic though generally less severely affected than men. We performed mutation analysis in 170 patients from 65 families and identified 55 different mutations. Our results confirm the wide molecular heterogeneity at this locus. Molecular study allows to confirm the diagnosis in male patients and the reliable diagnosis of heterozygous females in the family as biochemical tests (alpha-galactosidase A activity and urinary Gb(3) study) can be normal. However, in a few cases in which the index case is a female, it may remain difficult in the absence of an extensive familial study, to confirm (identification of a new missense the pathogenicity of which is unknown) or rule out (no gene alteration found) an heterozygote. Generally, genotype/phenotype correlations remain difficult as only a few mutations are more frequent. Furthermore, variations of the phenotype, even within the same family, suggest that other factors (genetic and epigenetic) could influence disease progression.