Beriberi is a nervous system ailment caused by thiamine (vitamin B1) deficiency. Thiamine is involved in the breakdown of energy molecules such as glucose. It is also found on the membranes of neurons. Symptoms of beriberi include severe lethargy and fatigue, together with complications affecting the cardiovascular, nervous, muscular, and gastrointestinal systems.
Symptoms of beriberi include weight loss, emotional disturbances, impaired sensory perception, weakness and pain in the limbs, and periods of irregular heart rate. Edema (swelling of bodily tissues) 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, a fourth form, gastrointestinal beriberi, was recognized in 2004:
- 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
- Gastrointestinal beriberi affects the digestive system and other bodily systems
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 (numbness) 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 (nystagmus)
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 (shortness of breath) on exertion
- Paroxysmal nocturnal dyspnea
- Peripheral edema (swelling of lower legs)
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. These 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
- Pale skin
- Ill temper
- Alterations of the cardiovascular system, especially tachycardia (rapid heart rate)
- Convulsions occasionally observed in the terminal stages
Gastrointestinal beriberi causes abdominal pain. Gastrointestinal beriberi is characterized by:
There are two major types of beriberi:
- Wet beriberi affects the cardiovascular system.
- Dry beriberi and Wernicke-Korsakoff syndrome affect the nervous system.
Eating a proper diet that is rich in thiamine and other vitamins will prevent beriberi. Nursing mothers should make sure that their diet contains all vitamins and be sure that infant formulas contain thiamine. People who drink heavily should try to cut down or quit, and take B vitamins to make sure their body is properly absorbing and storing thiamine.
A physical examination will reveal many of the early symptoms of beriberi, such as fatigue, irritation, nausea, constipation, and poor memory, but the deficiency may be difficult to identify. Information about the individual's diet and general health is also needed.
Untreated, beriberi is often deadly. With treatment, symptoms usually improve rapidly. Heart damage is usually reversible and is not permanent. Full recovery is expected. However, if acute heart failure has already occurred, the person's outlook is poor. Nervous system damage is also reversible, if caught early. If not, some symptoms (such as memory loss) may remain even with treatment.
Many people with 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 person with a thiamine-rich diet (e.g. whole grain brown bread) will lead to recovery, though at a much slower rate