Occipital horn syndrome was formerly considered a variant of Ehlers-Danlos syndrome. An X-linked recessive disorder, this variant is characterized by a deficiency in biliarycopper excretion that causes deformations in the skeleton. These include projections on the back of the skull (parasagittal bone exostoses arising from the occipital bone—the so-called "occipital horns") as well as deformities of the elbow, radial head dislocation, hammer-shaped lateral ends of the clavicles, and abnormalities of the hips and pelvis.
