MTPD is due to mutations in the HADHB subunit of the trifunctional enzyme complex, encoded by the genes HADHA or HADHB. Although pediatric forms are delineated from adult forms (as pediatric forms of FAODs show a more severe course manifesting with MM, hepatopathy, cardiomyopathy and sudden cardiac death (SCD) compared to adult forms, which usually go along only with isolated/pure MM), there is not much difference between them [4]. This evidence concerns the gene HADHB and mitochondrial trifunctional protein deficiency.