Siblings With Congenital Hyperinsulinism From Possible Parental Gonadal Mosaicism.

Congenital hyperinsulinism is the most common cause of persistent hypoglycemia in early infancy. Mutations in the gene for heterozygous hepatocyte nuclear transcription factor 4-alpha () account for approximately 5% of cases and are inherited in an autosomal dominant fashion or arise as de novo mutations. This case describes a unique presentation of parental gonadal, or germline, mosaicism as the suspected inheritance pattern for siblings with congenital hyperinsulinism caused by mutations.