Diagnosis: alopecia areata or not?

Alopecia areata is a common cause of hair loss in children and adults. In most cases, the diagnosis is straight forward and is easily made based on the patient's history and clinical presentation. However, in two specific scenarios, the diagnosis can be difficult and may require a scalp biopsy. We present four cases that illustrate these two problematic differentials: alopecia areata versus trichotillomania in adolescent females; and diffuse alopecia areata versus telogen effluvium versus androgenetic alopecia in adult women. Tables compare and contrast the clinical and histopathologic features of these nonscarring localized and diffuse alopecias.