Swiss Cheese Appearance of Dilated Follicular Infundibula in Trichotillomania

In a case study of a 32-year-old woman with a 2.5-year history of patchy hair loss and pruritus, a scalp biopsy revealed a 'Swiss cheese' appearance due to markedly dilated follicular infundibula filled with keratin, trichomalacia with broken and crumpled hair shafts, and numerous telogen/catagen hair follicles. These findings led to a diagnosis of trichotillomania. The 'Swiss cheese' appearance, previously considered a useful criterion for diagnosing alopecia areata, was observed in this case of trichotillomania, suggesting that it may not be specific to alopecia areata. The authors propose that the repeated rubbing of the scalp, which accompanies the twisting and twirling of hair in trichotillomania, could be the mechanism causing the dilation of follicular infundibula. This case contributes to the understanding that the 'Swiss cheese' appearance in histopathology may also be associated with trichotillomania, not exclusively with alopecia areata.