Mr. A, 19 years old, had been seen by local child psychiatrists since the age of 16 due to school difficulties and interpersonal problems. The medical records describe schizoid personality traits and explosive reactions, but never, in the past, had obsessions or compulsions been documented. He was currently hospitalized for the first time complaining about identity problems and social withdrawal. At admission, we observed reduced affective modulation, a marked reduction of thought production and some formal thought disturbances like incoherencies and thought blocks. No delirium or hallucinations were objectivated. In the beginning, schizophrenia simplex was suspected; thus, olanzapine 5 mg monotherapy was initiated and the dose was increased to 10 mg after 6 days. After 4 weeks of olanzapine treatment, Mr. A complained about intrusive obsessional images of buttocks of persons when talking with them, being unable to concentrate on the conversation. He increasingly had these obsessions also in the absence of persons, describing them as being like pornographic images, not being sexually exciting, but highly distressing. Over the following 2 weeks, the patient reported a steady worsening, the intrusions being almost continuously present and the patient avoiding almost every personal contact.