'Follicular Swiss cheese' pattern--another histopathologic clue to alopecia areata

Yellow dots are the most useful dermoscopic criterion in the clinical diagnosis of alopecia areata and correspond histopathologically with dilated follicular infundibula. They are found in about 95% of alopecia areata cases and help to differentiate alopecia areata from trichotillomania, telogen effluvium and from scarring alopecias. Histopathology of alopecia areata differs with disease activity and dermatopathologist, therefore, heavily depends on other diagnostic features. Objective of the study was to determine the frequency of dilated follicular infundibula, peribulbar lymphocytic infiltrate, inflammatory infiltrates of lymphocytes and eosinophils within fibrous streamers and a shift to catagen/telogen follicles in alopecia areata. Histopathologic features of 56 specimens of 33 patients were correlated with clinical findings and alopecia areata subtype.

57% of all biopsies showed dilated follicular infundibula, regardless of horizontal or vertical sectioning of the slides. Dilated follicular infundibula showed a maximum occurrence of 66% in the recovery stage of alopecia areata and were seen in 33% of alopecia areata incognita. In conclusion, dilated follicular infundibula, reminiscent of a Swiss cheese in horizontally sectioned slides, is an exceedingly useful criterion in the histopathologic diagnosis of alopecia areata and are of great help in the daily routine to recognize alopecia areata.