A guide to distinguish alopecia areata from other hair loss diseases presenting similar clinical manifestations

Alopecia areata (AA) is a commonly encountered autoimmune-mediated hair loss disease clinically characterized by well-demarcated hair loss patches and histologically by dense peribulbar lymphocytic cell infiltration leading to the destruction of hair follicles. Because of its distinctive clinical presentation, other hair loss diseases presenting clear hair loss patches can be misdiagnosed as AA. Thus, the confirmation of AA diagnosis by the combination of diagnostic approaches, including physical examination, hair pull test, trichoscopy, and skin biopsy is important. Trichotillomania (TT), scarring alopecia (represented by lichen planopilaris and chronic lupus erythematosus), tinea capitis, and triangular alopecia can manifest hair loss patches or areas hardly distinguishable from those in AA. Such findings as the absence of hair shaft pluckability or atrophic changes in the hair bulb, microscopic detection of fungi within isolated plucked hair shafts should be helpful to distinguish the aforementioned non-AA hair loss diseases from AA. Trichoscopic detection of follicular microhemorrhage, V-sign, and flame hairs are useful for the diagnosis of TT, while loss of the hair ostia is typical for scarring alopecia. Triangular alopecia is less frequently encountered and is distinguished by the presence of vellus-like hairs with in clinically hair loss patches as detected by trichoscopy. AA may present hair loss pattern resembling those of androgenetic alopecia (AGA) and female patten hair loss (FPHL). Hair miniaturization may be observed in the recovery phase of AA and in AGA