Bitemporal Scalp Hair Loss: Differential Diagnosis of Nonscarring and Scarring Conditions.

Bitemporal hair loss can be a diagnostic challenge because several entities may affect this region of the scalp, including both scarring and nonscarring conditions. Although traction alopecia is the most common cause of bitemporal hair loss, no studies to date have outlined all of the potential causes. We sought to review nonscarring and scarring conditions that have a clinical presentation of bitemporal hair loss, including traction alopecia, telogen effluvium, female pattern hair loss, frontal fibrosing alopecia, central centrifugal cicatricial alopecia, and seborrheic dermatitis. A Google Scholar and PubMed literature search were conducted for this review. The keywords used in the search included the following: "traction alopecia", "telogen effluvium", "androgenic alopecia", "androgenetic alopecia", "female pattern hair loss", "alopecia areata", "frontal fibrosing alopecia", "central centrifugal cicatricial alopecia", and "seborrheic dermatitis". The scope of our search included all research articles published from 1957 to February 2019. In total, 94 articles regarding non-scarring and scarring hair loss were selected and included according to topic relevance. Exclusion criteria included articles that did not address the epidemiology and/or clinicopathologic or dermatoscopic findings of non-scarring and scarring forms of alopecia. Inclusion criteria included articles that addressed a clinical presentation of bitemporal hair loss; or addressed epidemiology, clinical presentation, dermatoscopic findings, and/or treatment. Bitemporal hair loss is a common and often distressing condition with a broad differential. Clinicians must be aware of the potential causes of bitemporal hair loss. Prompt diagnosis is essential to prevent further hair loss, especially in scarring conditions.