Defects in genes encoding the peroxisomal enzymes involved in ether lipid synthesis or required for their peroxisomal import result in severe autosomal recessive inborn disorders, called Rhizomelic chondrodysplasia punctata type 1 (PEX7 deficiency, OMIM 215100), type 2 (GNPAT deficiency, OMIM 222765), type 3 (AGPS deficiency, OMIM 600121), or disorder reminiscent of Rhizomelic chondrodysplasia punctata (FAR1 deficiency, OMIM 616154). This evidence concerns the gene GNPAT and hyperinsulinemic hypoglycemia, familial, 4.