Autosomal recessive causes of LV wall thickening include glycogen storage disease (GSD) type II [caused by acid α-1,4-glycosidase (GAA) deficiency], GSD IIIA (caused by amylo-1,6-glucosidade/debranching enzyme deficiency), and Friedreich’s ataxia caused by expansions—GAA triplet repeats—in the frataxin gene. This evidence concerns the gene FXN and hyperinsulinemic hypoglycemia, familial, 4.