Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by α-
galactosidase A (α-Gal A) deficiency. The progressive accumulation of
globotriaosylceramide results in life-threatening complications, including renal, cardiac, and
cerebrovascular diseases. The pharmacological chaperone
migalastat was recently approved as an alternative to
enzyme replacement therapy in patients with amenable mutations. In this article, we investigate the proportion of amenable mutations, related to phenotype, in a population of adult patients with FD in Switzerland. This study included 170 adult patients (n = 64 males) from 46 independent pedigrees with 39 different identified mutations over the last 59 years. Overall, 68% had the classic phenotype and 48% fulfilled the current amenability criteria.
Migalastat was stopped in 2/11 (18%) patients: the only male classic patient, because of lack of efficacy based on
lyso-Gb3 levels, and one patient with a benign variant. In males, the achieved
enzyme activities in peripheral leucocytes under
migalastat treatment differed from the activities in HEK-cells after incubation with
migalastat (eg, 33% in PL vs 41% HEK-cells for p.F113L; 43% in leucocytes vs 36% in HEK-cells for p.N215S, 24-30% in leucocytes vs 96% in HEK-cells for S238N). In this national cohort, we found a relatively high proportion of patients with amenable GLA mutations, which, however, had heterogeneous extent of amenability: the higher the residual α-Gal A activity, the higher the chaperone effect. Further studies are required to investigate the long-term benefits of
migalastat therapy depending on the achieved
enzyme activities in different amenable mutations.