Beriberi is a disease caused by a deficiency of thiamine, or vitamin B1, that is expressed in three major clusters of symptoms, which vary from person to person. It involves edema, or swelling, of the legs, arms, and face. The nerves may be affected, causing, first, a loss of sensation in the peripheral nerves and, later, paralysis. The cardiovascular system may be involved, evidenced by enlargement of the heart and extremely low diastolic blood pressure. Beriberi may be chronic and so low-grade that it cannot be detected by clinical examination; in its chronic form, it may alternatively result in disability for months or years; or it may be acute and result in death in a few weeks. Until major tissue damage occurs, it is curable and reversible by consumption of thiamine.

The name “beriberi” derives from a Sinhalese word, meaning weakness. As kakke, it has been known in Japan since antiquity and is described in the earliest Chinese medical treatises. The several forms of beriberi have often been considered as separate diseases. In “wet” beriberi, swelling and heart complications occurred, although often with loss of the sense of touch, pain, or temperature. In “dry” beriberi, there was little swelling, but instead a progressive loss of those senses and then of motor control followed by atrophy of the muscles of the paralyzed limbs and a general wasting syndrome. Today it is thought that dry beriberi was partly due to a deficiency of vitamin B2. Shoshin beriberi was a term used to denote a fulminating, or acute form with severe heart complications.