Xeroderma pigmentosum is a rare genetic defect in ultraviolet radiation induced DNA repair mechanisms; characterized by severe sensitivity to all sources of UV radiation (especially sunlight). There are a wide range of symptoms, including blindness and deafness, blistering or freckling on minimum sun exposure, developmental disabilities, dwarfism and hypergonadism, increased skin and eye cancers, and mental retardation. The disease is life threatening because the DNA damage is cumulative and irreversible. There is no cure.
Xeroderma pigmentosum is very rare with less than 1,000 cases known worldwide.