FUCA1 and hyperinsulinemic hypoglycemia, familial, 4: Therefore, it has been postulated that other genetic, nongenetic and/or environmental factors, and not only FUCA1 mutations (since almost all cases of fucosidosis to date were linked to FUCA1 mutations and α-L-fucosidase deficiency), also underlie the heterogeneity of the clinical manifestations of the disease [11].