Beriberi refers to a cluster of symptoms caused primarily by a nutritional deficit in vitamin B1 (thiamine). Beriberi has conventionally been divided into three separate entities, relating to the body system mainly involved (peripheral nervous system or cardiovascular) or age of person (infantile). Beriberi is one of several thiamine-deficiency related conditions which may occur concurrently, including Wernicke's encephalopathy (mainly affecting the central nervous system), Korsakoff's syndrome (amnesia with additional psychiatric manifestations), and Wernicke-Korsakoff syndrome (with both neurologic and psychiatric symptoms).