Background: When biopsy specimens lack a "swarm of bees" peribulbar lymphoid infiltrate, the diagnosis of alopecia areata depends on the recognition of other histologic features of the disease.
Objective: Our objective was to determine the frequency of the presence of eosinophils in biopsy specimens of alopecia area'a in relation to the other major histologic features of the disease.
Methods: Biopsy specimens from 71 patients with alopecia areata were studied.
Results: Eosinophils were present in 38 of the 71 cases. A peribulbar lymphoid infiltrate was absent in 27 of the 71 cases. Eosinophils were present in 13 of these cases. Multiple catagen hairs and pigment casts (features which may lead to confusion with trichotillomania) were present in 39 cases. The presence of eosinophils was found to be a helpful diagnostic feature in cases with potential for misdiagnoses as trichotillomania.
Conclusion: Eosinophils are common in all stages of alopecia areata, both within the peribulbar infiltrate and within fibrous tracts. A "swarm of bees" peribulbar infiltrate may be absent. The presence of eosinophils is a helpful diagnostic feature of alopecia areata.