The incidence of GALK deficiency ranges between 1:150,000 and 1:1,000,000 (Sangiuolo et al., 2004), while the frequency of GALE deficiency varies from 1:6,200 to 1:64,800 depending on the ethnic background (Alano et al., 1998). Here, GALE is linked to hyperinsulinemic hypoglycemia, familial, 4.