The Intriguing Diagnosis of Lung Cancer in a Psychiatry Inpatient Unit: A Reflection Through a Case Report.

People with intellectual developmental disorders are vulnerable to somatic and mental illnesses, often presenting with behavioural changes. Through an intriguing and uncommon case report, we aim to provide an overview of behavioural changes in patients with an intellectual developmental disorder, emphasizing the need for screening for non-psychiatric conditions. We present a clinical case of a 57-year-old man with a personal history of intellectual developmental disorder, epilepsy, and alcohol and tobacco abuse. He had a previous acute psychiatric admission in 2017 due to behaviour disorganization and irritability. In April 2019, he was readmitted with disorganized behaviour and caregiver exhaustion. On the 58th day of hospitalization, he fell off his bed and suffered a mild traumatic brain injury. A cerebral CT scan revealed two metastatic lesions in the brain. Further investigations discovered a primary neoplastic lung lesion with metastasis to pulmonary lymph nodes. This case emphasizes that despite a long follow-up with psychiatry services, physical illness should be considered when patients with intellectual developmental disorders present with behavioural changes as they can precede image and laboratory findings. Additionally, further studies are needed in order to provide guidelines and proper medical and psychosocial care for this particular population and the caregivers.