Refractory alopecia areata with single hairs imitating frontal fibrosing alopecia: a prospective observational study.

Abstract

Lonely hair sign is considered as a clue to the diagnosis of frontal fibrosing alopecia (FFA). To report an undescribed variant of alopecia areata (AA) with which the patient developed single hairs and other features similar to FFA and to determine the underlying mechanism. We conducted a prospective observational study in patients who presented with receding hairline and single hairs, evaluating the clinical, trichoscopic, and histological features and their correlation. Immunochemistry studies were performed to describe the microenvironment. Eighteen patients were enrolled in the study. Despite the similarity to FFA clinically, these patients showed different histopathology which revealed a normal number of pilosebaceous units, one anagen hair in one or more pilosebaceous units, and others in telogen stage, consistent with single hairs under the naked eye or under trichoscopy. The severity of the hair loss assessed by SALT was no more than 50, but the response to conventional therapy was poor. This study reports a unique variant of AA. The pathological basis is an increase in the telogen hair follicles, with one anagen hair in one or more pilosebaceous units. Minimal inflammation consisting of CD3+ T lymphocytes and mast cells was demonstrated in the microenvironment.