SLC39A8 and congenital disorder of glycosylation: Moreover, SLC39A8 deficiency (type II congenital disorder of glycosylation (CDG)) is a severe metabolic disorder caused by impaired manganese metabolism in humans, leading to multi-organ involvement and symptoms such as cranial synostoses with lacunar skull, cerebral and cerebellar atrophy, severe psychomotor disability, seizures, and vision and hearing impairment [43,44,45].