Pelizaeus-Merzbacher disease: cellular hypersensitivity to ultraviolet light.

We report two connatal cases of Pelizaeus-Merzbacher disease (PMD) with cellular ultraviolet (UV)-hypersensitivity. We studied the UV-sensitivity of cultured fibroblast cells derived from these PMD cases, as compared with UV-sensitive Cockayne syndrome (CS) and xeroderma pigmentosum (XP) cells as positive controls. The ability of the PMD cells to form colonies after UV irradiation was intermediate between those of CS cells and normal controls. There were no differences in both colony-forming ability after x-ray irradiation and unscheduled DNA synthesis (UDS) activity after UV irradiation between the PMD cells and the control cells. These cytological results suggest the possibility that a DNA defect might be involved in PMD.