The policy, which has not yet included dermatological disorders, is being reviewed to incorporate three specific conditions: epidermolysis bullosa (EB), xeroderma pigmentosa (XP), and ichthyosis.

Five of the conditions (xeroderma pigmentosum, Cockayne's syndrome, trichothiodystrophy, Down syndrome, and triple-A syndrome) display a defect in the nucleotide excision repair pathway ...