Xeroderma pigmentosum.

Xeroderma pigmentosum is a rare disorder transmitted in an autosomal recessive manner. Xeroderma pigmentosum is based on a genetic defect in the DNA repair system. This disease manifests in early childhood. Patients with xeroderma pigmentosum have a marked sensitivity to sunlight and develop serious sunburns with onset of poikilodermia in the light-exposed skin. Squamous cell carcinomas, basal cell carcinomas and malignant melanomas already appear in childhood. The majority of patients die before reaching adulthood because of metastases. Genetically, xeroderma pigmentosum is divided into 7 complementation groups (XP-A to XP-G) and the xeroderma pigmentosum variants (XP-V). Diagnostically, assignment to the specific complementation group is made according to the fusioning of xeroderma pigmentosum fibroblasts. Differential diagnosis must distinguish xeroderma pigmentosum from other so-called DNA-repair-deficiency syndromes like the Cockayne Syndrome and trichothiodystrophy. Currently, there are reports of successful application of a topical DNA Repair Enzyme. This is a recombinant liposomal encapsulated T4 endonuclease V, which repairs UV-induced cyclobutan-pyrimidine dimers. In future, causal therapy could be based on gene therapy. The introduction of an intact repair gene which specifically codes the repair protein, could open new possibilities in the treatment of xeroderma pigmentosum.