Diagnostic usefulness of a peribulbar eosinophilic infiltrate in alopecia areata.

IMPORTANCE The histopathologic diagnosis of alopecia areata (AA) may be difficult in the chronic stage in which the presence of a peribulbar lymphocytic infiltrate is not definite. An eosinophilic infiltrate has been reported as a relatively common histopathologic finding and a helpful diagnostic feature in AA. OBJECTIVE To investigate the frequency and diagnostic usefulness of an eosinophilic infiltrate around the hair bulbs or within the fibrous tracts during the chronic stage of AA. DESIGN, SETTING, AND PARTICIPANTS A retrospective review was conducted at Chungbuk National University Hospital. A total of 162 scalp biopsy specimens of AA were analyzed. MAIN OUTCOMES AND MEASURES The frequency of a peribulbar eosinophilic infiltrate in AA. RESULTS In 30 of 162 specimens (18.5%) of AA in all stages, eosinophils were found around the hair bulbs with variable density but were not identified in the fibrous tracts of any specimen. Eosinophils around the hair bulbs were detected in 24 of 78 specimens (30.8%) of the acute stage of AA in which a peribulbar lymphocytic infiltrate was present, and eosinophils were densely infiltrated in 6 of these specimens (7.7%). In contrast, in the chronic stage of AA in which a peribulbar lymphocytic infiltrate was sparse or absent, eosinophils around the hair bulbs were found in only 6 of 84 specimens (7.1%); furthermore, eosinophils were sparsely present in all specimens. Pigmentary incontinence around the hair follicles was found in 58 of 84 specimens (69.0%), follicular miniaturization in 52 (61.9%), and shift to the catagen or telogen phase in 46 (54.8%). CONCLUSIONS AND RELEVANCE An eosinophilic infiltrate around the hair bulbs or within the fibrous tracts is not a common finding in the histopathologic characteristics of AA, especially in the chronic stage of the disease. Thus, the diagnostic usefulness of the eosinophilic infiltrate is limited to few cases of AA in the chronic stage. Other histopathologic findings, such as pigmentary incontinence around the hair follicles, follicular miniaturization, and shift to the catagen or telogen phase, are more useful diagnostic features in the cases of AA not showing a definite peribulbar lymphocytic infiltrate.