xeroderma pig·men·to·sum 
(pĭg′mən-tōsəm)
(pĭg′mən-tōsəm)n.
A rare hereditary skin disorder caused by a defect in the enzymes that repair DNA damaged by ultraviolet light.
[New Latin xēroderma pigmentōsum : xēroderma, xeroderma + pigmentōsum, neuter of pigmentōsus, of pigment.]