Alopecia and hair disorders in children — branching viva

Opening — framing the problem

The examiner begins: an eight-year-old has a three-week history of a coin-sized, completely bald, smooth patch behind the left ear, with no scale, no redness and a few tapering exclamation-mark hairs at the edge. Talk me through your approach. [1]

I would frame this as alopecia areata. The completely smooth, non-scaly bald patch with exclamation-mark hairs at the edge is the signature of an autoimmune attack on the anagen hair bulb, and the dermoscopy I would expect to see, yellow dots, black dots and short regrowing vellus hairs, supports it. The absence of scale, broken stubs and lymphadenopathy distinguishes it from tinea capitis at the bedside. [1]