For example, occipital horn syndrome is clinically and biochemically similar to Menkes disease, but with a less severe neurologic phenotype.36,37 Other pathogenic ATP7A alleles lead to an isolated distal motor neuropathy.38 Individuals affected by this neuropathy present with normal levels of ATP7A mRNA and protein and no signs of systemic Cu deficiency. Here, ATP7A is linked to occipital horn syndrome.