Lesson to Learn From Cellular infiltrate in Scalp Biopsy of Alopecia Areata

Background Alopecia areata (AA) is a common cause of hair loss. It is mediated by T lymphocytes. Scalp biopsy findings in AA differ according to the disease phase and activity. Objectives To study the cellular infiltrate in the transverse section of scalp biopsy of AA at different disease stages and in relation to disease activity. Methods The study was performed on 40 subjects with AA. A 4-mm punch biopsy was obtained from an AA scalp lesion. Biopsies were sectioned horizontally; 2 anatomical levels were studied (mid dermal and deep dermal levels). Results Ninety-five percent of AA showed noncicatrical alopecia. A significant relation was found between the course of AA and the terminal:vellus ratio. Peribulbar lymphocytic infiltration was seen in 70% of cases. Mast cells were observed in 87.5% of cases, including fibrous tract and around the arrector pili muscles. Eosinophils were detected in the scalp biopsy of 22.5% of cases. Course and activity of AA were significantly related to the peribulbar lymphocytic cell infiltration but not to mast cells and eosinophils. Conclusion Although a peribulbar lymphocytic infiltrate is the classical finding of AA, it is absent in the chronic phase. Mast cells are commonly found in the scalp biopsy of AA and could explain the potential therapeutic effect of antihistamines.