“His scalp is showing” was the delicate phrasing of a ten-year-old boy's mother. We learned that three months ago he had developed three perfectly round areas of perfectly bald skin on the right side of his scalp. They were totally symptomless, and not inflamed, looking like totally normal skin. Around the edges we could see tiny short hairs that looked like exclamation points. These helped confirm the diagnosis of alopecia areata.

The hair had simply suddenly fallen out without a trace. This was not the hair loss of lupus erythematosus, which is inflammatory, or the hair loss of ringworm with its broken hairs. This was not the hair loss of trichotillomania where the child plucks out his own hairs in frustration, leaving a tell-tale stubble of very short hairs (too short to pull).

No, this was an autoimmune condition known as alopecia areata. Somehow, the body rejects the hairs without any sign of obvious inflammation. As the hair follicles stumble to recovery around the edges, short atrophic exclamation point hairs are produced, constricted at the base in a sputtering regeneration.

We did not need a skin biopsy for diagnosis, but we needed to study him for a cause. Although alopecia areata is classified as an autoimmune disease, and thus a rejection phenomenon, we know from experience that a focus of infection may trigger such hair loss. What was this boy's source of infection? We did not have to look far.