Patients with XP, XP/CS, CS, or TTD of any age, gender, race or HIV status are eligible for this study. Patients will be sought by contacting professional organizations (such as the American Academy of Dermatology-XP Task Force), lay support groups (such as the XP Society and the Share and Care CS Support Network) or by direct referral.
On referral, patients will be considered for inclusion in the study:
If they have clinical documentation of typical features of XP, XP/CS, CS or TTD or;
If they have laboratory documentation of defective DNA repair, or;
If they have some suggestive clinical features and are willing to participate in the study.
Inability or unwillingness to provide tissue (skin, blood, buccal cells or hair) for laboratory studies.