PNPT1 and mitochondrial DNA depletion syndrome: Analysis of inheritance patterns revealed compound heterozygous variants in six patients for the following genes (associated autosomal recessive disorders are shown in parentheses): GFM1 (combined oxidative phosphorylation deficiency 1), SUCLA2 (mitochondrial DNA depletion syndrome 5), PNPT1 (combined oxidative phosphorylation deficiency 13), CPS1 (Carbamoyl-phosphate synthetase 1[CPS1] deficiency), COQ4 (primary coenzyme Q10 deficiency), and ERBB3 (lethal congenital contracture syndrome type 3).