Peripheral neuropathy in four cases of group A xeroderma pigmentosum.

We describe the clinical features and findings of biopsied sural nerves of 4 cases of xeroderma pigmentosum. Nine genetic forms of xeroderma pigmentosum have been reported by complementation studies. These four cases were diagnosed as Group A xeroderma pigmentosum by complementation studies using cultured skin fibroblasts. All cases had delayed mental and motor development in areas such as head control over 4 months of age and walking without support over 18 months of age. Three cases had the gradual onset of a gait disturbance between 6 and 9 years of age. Motor conduction velocity and sensory conduction velocity of the ulnar nerve were slightly delayed. The sural nerve of the slightly impaired patient showed a normal density of myelinated fibers, but a selective reduction of the large myelinated fibers with zebra-body-like structures in Schwann cell cytoplasm. The population density of all nerve fibers was severely diminished in the severely impaired cases. Ultrastructural observation disclosed many denervated Schwann cells and pockets of collagen isolated by loops of denervated Schwann cell cytoplasm. These findings suggest that the degenerative process in peripheral nerves of xeroderma pigmentosum is axonal. Peripheral neuropathy in Group A xeroderma pigmentosum resembles that of patients with ataxia telangiectasia who are known to have a defect in the repair mechanisms of their DNA in cultured skin fibroblasts.