Thiamine deficiency

Thiamine deficiency occurs when the body has too little vitamin B1. When the condition becomes severe and long-lasting, it is called beriberi. The name "beriberi" may have come from a Sinhalese phrase meaning "I cannot, I cannot," referring to the weakness it causes. In adults, there are two main types: wet beriberi, which harms the heart and blood vessels and leads to a rapid heartbeat, shortness of breath, and swollen legs; and dry beriberi, which damages the nervous system and causes numbness in the hands and feet, confusion, leg pain, and trouble moving the legs. A form with loss of appetite and constipation can also occur. Acute beriberi, mostly seen in babies, brings loss of appetite, vomiting, lactic acidosis, changes in heart rate, and an enlarged heart.

Risk factors include eating mostly white rice, alcoholism, dialysis, chronic diarrhea, and taking high doses of diuretics. Rarely, a genetic problem with absorbing thiamine from food is the cause. Wernicke encephalopathy and Korsakoff syndrome are types of dry beriberi. Diagnosis relies on symptoms, low thiamine in the urine, high blood lactate, and improvement after taking thiamine supplements. Treatment involves thiamine given by mouth or injection, and symptoms usually resolve within a few weeks. Fortifying food can prevent the disease at the population level.

Thiamine deficiency is rare in most developed countries but remains common in sub-Saharan Africa. Outbreaks have occurred in refugee camps. The condition has been known in Asia for thousands of years and became more frequent in the late 1800s as rice processing increased.

**Signs and symptoms** Beriberi symptoms include weight loss, emotional disturbances, impaired sensation, weakness and pain in the limbs, and irregular heart rate. Swelling of body tissues is common. Blood levels of lactic acid and pyruvic acid may rise. In advanced cases, high-output heart failure and death can occur. Symptoms may appear alongside those of Wernicke's encephalopathy, a neurological condition linked to thiamine deficiency. Beriberi is divided into four categories: dry beriberi (affects the peripheral nervous system), wet beriberi (affects the cardiovascular system), infantile beriberi (affects babies of malnourished mothers), and gastrointestinal beriberi (affects the digestive system, recognized in 2004).

**Dry beriberi** Dry beriberi causes wasting and partial paralysis from damaged peripheral nerves. It is also called endemic neuritis. Signs include difficulty walking, tingling or numbness in the hands and feet, loss of tendon reflexes, loss of muscle function or paralysis of the lower legs, mental confusion, speech difficulties, pain, involuntary eye movements, and vomiting. A selective loss of large proprioceptive sensory fibers without motor impairment can lead to sensory ataxia—a loss of balance and coordination due to missing position sense.

**Brain disease** Wernicke's encephalopathy, Korsakoff syndrome (also called alcohol amnestic disorder), and Wernicke–Korsakoff syndrome are forms of dry beriberi. Wernicke's encephalopathy is the most common thiamine deficiency condition in Western society, though it can also occur in people with poor nutrition from gastrointestinal disease, HIV/AIDS, or from giving intravenous glucose or hyperalimentation without enough B vitamins. It is a neuro-psychiatric disorder marked by eye movement paralysis, abnormal stance and gait, and severe mental disturbance. Korsakoff syndrome usually follows Wernicke's encephalopathy and involves retrograde and anterograde amnesia, impaired conceptual thinking, and reduced spontaneity. Alcoholics often develop thiamine deficiency due to inadequate nutritional intake, decreased thiamine absorption from the gut (active transport into enterocytes is disrupted by acute alcohol exposure), reduced liver stores from fatty liver or fibrosis, and impaired thiamine use (magnesium, needed for thiamine to bind to enzymes, is also low). Alcohol itself blocks thiamine transport in the gut and prevents its conversion to the active cofactor form. With better nutrition and stopping alcohol, some impairments—especially brain function—can reverse, though severe Wernicke–Korsakoff syndrome leaves permanent damage.

**Wet beriberi** Wet beriberi affects the heart and circulatory system and can be fatal. It causes a combination of heart failure and weakened capillary walls, leading to swelling of peripheral tissues. Signs include increased heart rate, vasodilation that lowers systemic vascular resistance and causes high-output heart failure, and elevated jugular venous pressure.