PDP1 and hyperinsulinemic hypoglycemia, familial, 4: Mitochondrial diseases represented a unique situation in our cohort in that none of our patients were identified to have mitochondrial DNA mutations, which is consistent with the autosomal recessive mode of inheritance and suggestive of nuclear rather than mitochondrial DNA mutation.45, 46 Three patients were confirmed to have PDH deficiency on cultured skin fibroblasts.