The Milder Allelic Form, Occipital Horn Syndrome, in Contrast to the More Severe Form, Menkes Disease, is caused by Very Small Amounts of Normal ATP7A Transcript

The gene ATP7A encodes for the copper-transporting ATPase ATP7A, important for regulating copper [Cu (I)] level in the cells. In the small intestine, the ATP7A protein helps controlling the absorption of Cu (I) from food. The ATP7A gene contains 23 exons. Pathogenic variants in the gene, ATP7A, results in two different copper-deficiency disorder, occipital horn syndrome (OHS; OMIM #304150) and the more severe form, Menkes disease (MD; OMIM #309400).