A 25-year-old patient reported to a 24-hour psychotherapy unit with a suspected avoidance personality. He complained of fear of people, social situations, a feeling of being misunderstood, and difficulties in maintaining work. A special way of building relationships with other patients was observed during the treatment. He lacked interest in the group members and the psychotherapy. During group sessions, he remained thoughtful and non-empathetic. His comments were bizarre and controversial. The diagnostic hypotheses oscillated from personality disorders to ADHD and Asperger syndrome. After an interview with his family and a reliable diagnosis combining psychiatric, psychological, neuropsychological, and physical examination, he was diagnosed with “overall disorders of unspecified development”. Initially assessed by the group as anti-social, he received the necessary help due to defining the diagnosis and psychotherapeutic interventions. The article points out the difficulties in diagnosing adults with ASD and the need for careful diagnosis and interdisciplinary cooperation shortening the patient’s suffering.