Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. XEroderma pigmentosa, or XP, is an autosomal recessive genetic disorder of DNA repair in which the ability to repair damage caused by ultraviolet (UV) light is deficient. IN some extreme cases, those affected by the disease are able to be subjected to no sunlight at all, no matter how small. MUltiple basal cell carcinomas (basaliomas) and other skin malignancies frequently occur at a young age in those with XP. IN fact, metastatic malignant melanoma and squamous cell carcinoma are the two most common causes of death in XP victims. XP Is roughly six times more common in Japanese people than in other groups. THe most common defect in xeroderma pigmentosum is an autosomal recessive genetic defect in which nucleotide excision repair (NER) enzymes are mutated, leading to a reduction in or elimination of NER.