The 45-year-old male patient described in this case report had a classic case of pellagra. The patient was initially brought to a psychiatric hospital because of disorderly behavior. On admission the patient was unable to provide a history so he was given a provisional diagnosis of Psychosis Not Otherwise Specified. Despite having the cardinal symptoms of dermatitis, dementia and (three days after admission) diarrhea it took 20 days to confirm the diagnosis of pellagra. After initiation of appropriate treatment it took about six months for the patient to make a complete recovery.