Traumatic alopecia in trichotillomania: a pathogenic interpretation of histologic lesions in the pilosebaceous unit

Ten patients with traumatic alopecia (trichotillomania) were being investigated histologically and, in five of them, hairs from the affected scalp area were plucked out for direct microscopic examination. Some histologic features appear to be specific markers for traumatic alopecia: empty hair ducts, plucked out hair bulbs, clefts in hair matrix, catagen involution of empty outer root sheaths, Miescher's trichomalacia in the deep dermis and torn-off sebaceous glands. Other signs are unspecific, such as presence of catagen and anagen VI hairs, infundibular plugging, melanin in keratin plugs and in the dermal papilla. The relative frequency of the different histopathologic features was evaluated. When little clinical information is available, a diagnosis of traumatic alopecia can be supported by skin biopsy. The histologic picture of trichotillomania is always incomplete, depending upon factors such as intensity of pulling or/and time of biopsy after plucking.