6.1.2 Xeroderma Pigmentosum
Grading & Level of Importance: C
From about 1 in 500,000 live births in Western Europe to much higher frequencies in Japan and North Africa.
Group of uncommon genodermatoses with markedly increased light sensitivity and tendency towards developing actinic damage and malignant skin tumours.
Aetiology & Pathogenesis
Autosomal recessive inherited defects in DNA excision repair enzymes. Cells cannot repair UV-induced damage.
Signs & Symptoms
Marked photosensitivity with acute photodermatitis and marked actinic damage, multiple lentigines, including actinic keratoses, squamous cell carcinomas, basal cell carcinomas, malignant melanomas, poikiloderma, skin atrophy. Eyes also suffer UV damage. Some types (DeSanctis-Cacchione syndrome) have neurological findings.
Generalised; visible symptoms in UV light-exposed areas.
Types A-G dependent on type of gene defect.
Laboratory & other workups
Identification of endonuclease and other repair enzyme defects in cultured fibroblasts, DNA sequencing of known genes.
According to light induced skin damage and type and stage of tumor.
Reduced life expectancy starting already in the first life decade and depending on defect. Development of multiple malignant skin tumours, especially squamous cell carcinomas and malignant melanomas.
Development of malignant skin tumours (squamous cell carcinoma, basal cell carcinoma, malignant melanoma) before 20 years of age.
Clinical findings (photosensitivity, early actinic damage), genetic analysis, family history.
Xeroderma pigmentosum variants with same phenotype, later onset, no genetic defects (pigmented xerodermoid).
Prevention & Therapy
Consequent avoidance of UV exposure. Early use of high-potency broad-spectrum sunscreens, close clinical control, prompt tumour excision. Systemic retinoids for prophylaxis. Vitamin D supplementation.
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