Definition:

Occipital horn syndrome (OHS), formerly known as Ehlers-Danlos syndrome type IX or X-linked cutis laxa, is a mildest form of Menkes disease (MD). MD and OHS are X-linked recessive disorders of impaired copper metabolism due to mutations in the ATP7A gene. The patients with classical MD have severe developmental and neurological impairments due to subnormal amount of copper in the brain and a variety of symptoms such as connective tissue abnormalities, tortuosity of blood vessels and peculiar hair. Most of the classical MD patients die before the age of 3 years. On the other hand, the neurological symptoms of OHS patients are milder and lead to a clinical picture mainly characterized by connective tissue manifestations and skeletal abnormalities that include occipital exostoses, which give rise to the syndrome's name. These patients have normal or close-to-normal cognitive functions.