In a similar manner, dystonic head tremor observed in AFG3L2-spinocerebellar ataxia type 28 (129), GBA2-Autosomal recessive spastic paraplegia type 46 (130), PEX6-Peroxin 6 deficiency (131), PEX16- Peroxin 16 deficiency (132), Niemann Pick type C disease (12), NAXE-NAD(P)HX epimerase deficiency (133), TTPA-vitamin E deficiency (55), and SCP2-Sterol carrier protein-2 deficiency (74) gives an excellent clue for the diagnosis of the IEMs. This evidence concerns the gene PEX16 and spinocerebellar ataxia type 28.