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 patient (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)
The main cause is inadequate nutrition. Historically, beriberi has been endemic in regions dependent on what is variously referred to as polished, white, or de-husked rice. This type of rice has its husk removed in order to extend its shelf life, but also has the unintended side-effect of removing the primary source of thiamine. Beriberi caused by inadequate nutritional intake is rare today in developed countries because of quality of food and the fact that many foods are fortified with vitamins. There are no reliable statistics for beriberi in developed countries in the 19th century or earlier; neither are statistics available before the last century in countries in extreme poverty.
Beriberi is a recurrent nutritional disease in detention houses even in this century. High rates of illness and death in overcrowded Haitian jails was traced in 2007 to the traditional practice of washing rice before cooking. War refugees or the people who live in countries which experience famine can be affected by this and other nutritional disorders. Beriberi can also be masked by other famine and nutritional deficiency disorders.
Sign and Symptoms
Symptoms of beriberi include weight loss, emotional disturbances, impaired sensory perception, weakness and pain in the limbs, and periods of irregular heart rate. Edema is common. It may increase the amount of lactic acid and pyruvic acid within the blood. In advanced cases, the disease may cause high output cardiac failure and death. Symptoms may occur concurrently with those of Wernicke's encephalopathy, a primarily neurological thiamine-deficiency related condition.
Beriberi is divided into three historical classifications:
- Dry beriberi specially affects the peripheral nervous system
- Wet beriberi specially affects the cardiovascular system and other bodily systems
- Infantile beriberi affects the children of malnourished mothers.
Dry beriberi causes wasting and partial paralysis resulting from damaged peripheral nerves. It is also referred to as endemic neuritis. It is characterized by:
Difficulty in walking
Tingling or loss of sensation in hands and feet
Loss of tendon reflexes
Loss of muscle function or paralysis of the lower legs
Mental confusion/speech difficulties
Involuntary eye movements
A selective impairment of the large proprioceptive sensory fibers without motor impairment can occur and present as a prominent sensory ataxia, which is a loss of balance and coordination due to loss of the proprioceptive inputs from the periphery and loss of position sense.
Wet beriberi affects the heart and circulatory system. It is sometimes fatal, as it causes a combination of heart failure and weakening of the capillary walls, which causes the peripheral tissues to become edematous. Wet beriberi is characterized by:
Increased heart rate
Vasodilation leading to decreased systemic vascular resistance, and high output cardiac failure
Elevated jugular venous pressure
Dyspnea on exertion
Paroxysmal nocturnal dyspnea
Infantile beriberi usually occurs between two and six months of age in children whose mothers have inadequate thiamine intake. In the acute form, the baby develops dyspnea and cyanosis and soon dies of heart failure. The following symptoms may be described in infantile beriberi:
Hoarseness, where the child makes moves to moan but emits no sound or just faint moans, caused by nerve paralysis
Weight loss, becoming thinner and then marasmic as the disease progresses
Alterations of the cardiovascular system, especially tachycardia.
Convulsions occasionally observed in the terminal stages.
Thiamine in the human body has a half-life of 18 days and is quickly exhausted, particularly when metabolic demands exceed intake. Thiamine is a cofactor required for ATP synthesis and is, therefore, involved in a variety of glucose metabolism-related and neurological functions. After modification in the body to a diphosphate form, thiamine is involved in a vast array of functions:
Production of the neurotransmitters glutamic acid and GABA, through the citric acid cycle
Lipid metabolism, necessary for myelin production
Amino acid metabolism
Many patients of beriberi can be treated with thiamine alone. Given thiamine intravenously (and later orally), rapid and dramatic recovery can occur within hours. In situations where concentrated thiamine supplements are unavailable, feeding the patient with a thiamine rich diet will lead to recovery, though at a much slower rate.