This patient has alopecia areata, a chronic autoimmune disease that results in smooth, hairless patches of skin. Tapered “exclamation point” hairs may be seen at the periphery; these hairs have shafts that are thicker at the distal portion and narrower near the scalp. Older patients may demonstrate sparing of white/gray hairs, and in some patients the hair regrowth in existing patches begins with fine, white/fair hairs. The scalp is the most common site. Individual patches can spontaneously resolve within 12 months; however, new patches may develop. An autoimmune mechanism is supported by the increased rate of other autoimmune diseases, such as type 1 diabetes mellitus and autoimmune thyroid disease, in patients with alopecia areata as well in their family members.

Androgenetic alopecia is a type of diffuse nonscarring alopecia that can affect both men and women. In men, the bilateral temples and vertex are often affected. Androgenetic alopecia results in hair follicles that are thinner in caliber or “miniaturized” and loss of the hair follicle; however, androgenetic alopecia causes a decreased density of hair but not areas of complete loss of hair as seen in alopecia areata.

Discoid lupus erythematosus is the most common type of chronic cutaneous lupus. On the scalp, discoid lupus erythematosus manifests as scaling, erythematous, and hyper- and hypopigmented patches with alopecia. Multiple lesions are more likely than a single lesion.

Telogen effluvium is a diffuse nonscarring form of hair loss that is usually triggered by a systemically stressful event such as a serious illness, surgery, or childbirth. Approximately 3 to 5 months after the inciting event, numerous hairs are shed, leading to noticeably thinned hair. A small hair bulb may be visible at the scalp end of the shed hair. The hair loss tends to be patchy and diffuse; foci of total alopecia are not seen as in alopecia areata.

Tinea capitis causes scaling, inflammation, pustules, and pruritus, none of which are present in alopecia areata.