Delirium associated with vitamin B12 deficiency after pneumonia.

A case is presented of a 65-year-old man with chronic schizophrenia who, after four years of remission, developed psychotic symptoms after pneumonia. The patient was found to be deficient in vitamin B12. His psychosis remitted within 5 days of administration of vitamin B12 and folic acid. This case emphasizes the need to measure vitamin B12 in psychogeriatric patients, especially when they present with a severe infection and organic mental symptoms.