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Trichotillomania (TTM) is a psychiatric disorder can be triggered by traumatic events characterized by recurrent hair pulling. The incidence of post-traumatic stress disorder (PTSD) in TTM patients was also significantly higher than in the normal population. It is estimated that serotonergic system, dopaminergic system, hypothalamic-pituitary-adrenal (HPA) axis genes may be related with PTSD and TTM co-occurrence. When the literature is reviewed it is seen that serotonergic system gene especially 5HT-2A gene polymorphism may play an important role as a com-mon possible genetic background in the etiology of posttraumatic stress disorder and trichotillomania. It was also observed that effective results were obtained when agents acting on 5HT-2A receptor were preferred in the treatment. Here, we report a 20-year-old male patient who was diagnosed with TTM and PTSD as a result of trau-matic life event a year ago and we also aimed to discuss a possible common genetic etiology which may cause this comorbidity. [Anadolu Psikiyatri Derg 2019; 20(1.000): 110-112]