الفهرس 
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Abstract
Alopecia areata (AA) is a common form of localized, non-scarring hair loss. It is characterized by the loss of hair in patches, total loss of scalp hair (alopecia totalis), or total loss of body hair (alopecia universalis). It is a common disease encountered by dermatologists, with a frequency ranging from 0.7% to 3.8% of patients attending dermatology clinics. One-third of patients will experience spontaneous remissions within the first year. Persistent moderate-to-severe AA causes significant disfigurement and psychological distress in affected individuals. The etiopathogenesis of the disease is still unclear, but it is hypothesized to be an organ-specific autoimmune disease mediated by T lymphocytes directed to hair follicles. Genetic predisposition and environmental factors may trigger the initiation of the disease. The aim of this study was to evaluate the role of OPN in pathogenesis of alopecia areata and to correlate its level with disease severity. Osteopontin is an acidic glycoprotein expressed by a variety of tissues and cell types, including immune cells. It exists in two distinct isoforms; secreted (sOPN) and/or intracellular (iOPN) protein. Secreted OPN exerts its effect by binding to the cell surface receptors, expressed by target cells. Osteopontin is multifunctional and its functions are linked to various physiological and pathological events. It has been identified as an important molecule involved in tissue repair, inflammation and