HSD17B10 and hyperinsulinemic hypoglycemia, familial, 4: The hypomethylation of the CpG island in the proximal promoter of the HSD17B10 gene provides additional evidence for the variable escape of the HSD17B10 gene from X-chromosome inactivation which could influence the range of severity of HSD10 deficiency, an inherited error in isoleucine metabolism, in heterozygous females.