How do I know if I have xeroderma pigmentsum?

Genetic Testing. There are several types of xp (xeroderma pigmentosa) all of which are related to genetic defects in the ability of cells to repair dna damage causes by uv (ultraviolet rays). Xp dramatically increases your risk for skin cancer. You should start with seeing a dermatologist and go from there. If there is suspicion you may have the disease, genetic testing will be required to confirm this.