Xeroderma pigmentosum (XP) is characterized by hyperphotosensitivity to the UV constituent of sunlight. The hallmark of XP is a predisposition to skin neoplasia, with a >1,000-fold incidence of UV-induced squamous cell carcinoma and malignant melanoma. Classical XP is caused by mutations in one of seven genes XPA-XPG.
El-Hefnawi and Smith (1965) and El-Hefnawi et al. (1965) presented useful Egyptian pedigrees, possibly of complementation groups A and C, and suggested linkage with the ABO blood group locus. Bootsma and Keijzer (1979) studied eight patients from six Egyptian families. Three were assigned to complementation group A and five to group C.
[Bootsma D, Keijzer W. Genetic analysis of xeroderma pigmentosum including Egyptian families. (Abstract) Cytogenet Cell Genet. 1979; 25:139.]
Hashem et al. (1980) conducted a survey of DNA repair characteristics among Egyptians with xeroderma pigmentosum. Out of 16 XP patients, biopsies from eight were analyzed for unscheduled DNA synthesis, strand breakage during pyrimidine dimer excision, and complementation groups. The patients were equally distributed between Complementation Groups A and C. Unscheduled synthesis and strand breaks were significantly higher in Group C than in Group A cells. Central nervous system disorders were found in all of the Group A patients and in none of the Group C patients. No clinical symptoms were observed in the heterozygotes. A 2-month-old sib of an XP patient was free of symptoms, but unscheduled synthesis and strand breakage in cultures from this sib were the same as in the related XP homozygote.