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Kallmann Syndrome (KS) is an uncommon disorder caused by a deficient production or secretion of gonadotropin-releasing hormone (GnRH) and manifests with an absence of spontaneous puberty and impaired sense of smell. Multiple inheritance patterns have been recognized in the etiology. KS and psychosis have occasionally been con-sidered to originate in similar predisposing genetic profile. Defective KAL-X gene which had previously been attributed in the etiopathogenesis of schizophrenia was asserted to lead to an impairment in the migration of GnRH neurons and olfactory deficits in various severity and disruption in sexual developmental, consequently. Our case is a 19-year-old male previously diagnosed with KS at his 13, who has been under the monthly intramuscular treat-ment of testosterone propionate and testosterone phenylpropionate at the dose of 250 mg. He was admitted to our clinic with auditory and visual hallucinations that started two years ago. Persecutory delusions, social isolation, and suicidal thoughts also existed. We diagnosed him schizophrenia with comorbid KS following the hospitalization and a detailed psychiatric examination. Olanzapine was initiated as 5 mg/day and potentiated to 15 mg/day. His delu-sions, hallucinations and suicidal thoughts had improved with the treatment. In this illustration, we purposed to discuss probable common etiopathogenesis underlying this comorbidity. [Anadolu Psikiyatri Derg 2018; 19(4.000): 427-430]