ADSL and hyperinsulinemic hypoglycemia, familial, 4: The high frequency of the ADSL variant c.1277G>A (p.Arg426His) has been demonstrated in Polish (50% of pathogenic alleles) and Czech (30%) patients with adenylosuccinate lyase deficiency; this allele is also often found among German patients but is not characteristic for other Slavic populations [59,60].