Newborn screening for Fabry disease in Japan: prevalence and genotypes of Fabry disease in a pilot study.

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by a deficiency of α-galactosidase A (GLA) activity. Enzyme replacement therapy (ERT) for FD is available, and newborn mass screening for FD is being implemented. Here, we undertook a pilot study of newborn mass screening for FD in Japan. GLA activity in dried blood spots was measured using a fluorescence assay and confirmed by measurement of GLA activity in white blood cells (WBCs) in infants with abnormally low GLA activity. This was followed up by genetic testing. A total of 21 170 neonates were enrolled in the study. Of these, seven (five boys, two girls) had low GLA activities, which were verified by the WBC GLA activity assay. Thus, the initial fluorescence assay was suitable for newborn mass screening for FD. Pathogenic mutations of the GLA gene, that is, V199M and IVS4+919G>A, were found in two boys and one boy, respectively. Functional mutations, E66Q and c.-10C>T: g.1170C>T, were found in two boys and one girl, respectively. The prevalence of test-positive newborns was 1/3024, while that of those with a pathogenic mutation was 1/7057. The numbers are higher than those previously anticipated. Standardized management for FD found during newborn mass screening, including an ERT regimen, remains to be established.