Splitting hairs: The 'hamburger sign' in trichotillomania

Background: A 43-year-old male presented with the clinical findings of patchy alopecia that contained persistent hair and re-growth of hairs of various lengths, consistent with trichotillomania. A biopsy was performed to confirm the diagnosis. Results: Histologic evaluation revealed findings consistent with trichotillomania, including trichomalacia. Several hair shafts also showed a vertically oriented split, which contained proteinaceous material and erythrocytes. Morphologically, these were reminiscent of a hamburger within a bun. Conclusions: The unusual finding reported in this case has not been previously reported. The "hamburger bun sign" provides an additional clue to traumatic injury in the evaluation of biopsies for trichotillomania.