Increased thickening of the skull base and calvaria, especially in the frontal and parietooccipital regions. Histopathologic findings include loss of nerve fibers and myelin sheath and atrophy of the retinal nerve and ganglion cells. Cold blue disproportionately long extremities and flexion contractures of the elbows, ankles, and knees. Kyphosis, ankylosis, and platyspondyly of the vertebral bodies. Seborrheic dermatitis may occur.
Subcutaneous fat is diminished over the entire surface of the body, except for suprapubic areas.
Growth retardation becomes evident during the second year and photodermatitis appears by the second year of life. Several cases have been reported with a much later onset, some in patients with normal intelligence. Choreoathetosis, sensorineural deafness, blindness, and unsteady gait. There appears to be a defect in DNA repair with hypersensitivity of CS cells to ultraviolet radiation and inability to restore RNA and DNA synthesis rates to normal after UV irradiation.