A mother brings her 12-year-old son to dermatology following a referral from the boy’s pediatrician. Several months ago, she noticed her son’s hair loss. The change had been preceded by a stressful period in which she and her husband divorced and one of the boy’s grandparents died unexpectedly.
Both the mother and other relatives and friends had observed the boy reaching for his scalp frequently and twirling his hair “absentmindedly.” When asked if the area in question bothers him, the boy always answers in the negative. Although he knows he should leave his scalp and hair alone, he says he finds it difficult to do so—even though he acknowledges the social liability of his hair loss. According to the mother, the more his family discourages his behavior, the more it persists.
EXAMINATION
Distinct but incomplete hair loss is noted in an 8 x 10–cm area of his scalp crown. There is neither redness nor any disturbance to the skin there. On palpation, there is no tenderness or increased warmth. No nodes are felt in the adjacent head or neck. Hair pull test is negative.
Closer examination shows hairs of varying lengths in the affected area: many quite short, others of normal length, and many of intermediate length.
Blood work done by the referring pediatrician—including complete blood count, chemistry panel, antinuclear antibody test, and thyroid testing—yielded no abnormal results.
What is the diagnosis?