الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Premalignant and malignant changes in skin result from repeated, prolonged exposure to sunlight . Basal cell carcinoma is the most common carcinoma of the skin. Sun exposure plays an important role in its development. Xeroderma pigmentosum is a rare autosomal recess¬ive disease and has ultraviolet hypersensitivity and abnormal DNA repair . DNA damage can be produced by exposure to UVR or other chemicals like porphyrin and the accumulation of this damage leads to carcinogenesis . Also the accu¬mulation of porphyrins in the skin with aging leads to photodynamic carcinogenesis . The purpose of this study was to evaluate the possible faults in repair of skin after actinic.’damage, taking in consideration the interaction that may occur between DNA synthesis and damaging effect of possible derangement in porphyrin metabolism . In the present work 25 patients with photosensi¬tive, premalignant and malignant skin diseases, xerod-erma pigmentosum and basal cell carcinoma, were randomly selected from the Outpatient Clinic of Dermatology in Mansoura University Hospital . All were submitted to.