الفهرس 
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Abstract
Alopecia areaa is a common skin disease its exact incidence is unknewn becouse cases thatare mild or have non-scalp involvement maynever to come to a pysician,s attention it accounts about 207%among patientsattending the dermatology outpatien clinic faculty of medicine alexandria university, during the years 1980 ,1981 and 1982 (ibrahim,1985) the etiology of he disease is still unknown however circumstantial evidence indicate that immunological (friedman1981a galbrait et al 1984( and genetic factors (porter and lobitz)1970muller 1973) are implicated in the pathogenesis ofalopecia areata the most consistent and convincing evidence that there is an abnormal cellular immune respponse to hair follicles in alopecia areata is the lymphocytic infiltrate around hair follicles the infiltrate first appears around bulbar blood vessels and thebulb of anagen hairs and infiltrates the matrix (bystryn and tamesis 1991) in normal skin the epidermal keratincoytes and follicular epithelium aredevoid of epidermal keratincoytes and follicular epithelium are devoid of human leukocyte antigen and intercellular adhesion molecule further evidence that cellular immune mechanisme are operating in alopecia areata has been provided by messenger and bleehen 1985 who demonstrated the aberrant expression of hla-dr antigen on theepitelial cells of the precortical matrix and presumptive cortex of anagen folliclesfrom lesional skinin alopecia areata in alopecia areata there is also an abnormal expressionof icam )gupta et al 1980).