beriberi

=Beri-beri=

What it is
Beriberi is caused by a deficiency of thiamine (vitamin B1), a water-soluble and heat-labile vitamin required for carbohydrate metabolism.

Dietary thiamine deficiency can be caused by an overall poor nutritional intake, by dietary customs that rely heavily on inadequate food sources (eg, milled rice), and, rarely, by consuming foods that contain thiaminases or antithiamine compounds. A cohort at particularly high risk are individuals with alcoholism with poor nutrition because alcohol also impairs thiamine absorption.
 * Risk Factors**

The prevalence of beriberi is much higher in East Asian countries because of the consumption of milled rice. Thiamine is contained in the outer coat of rice, and polishing destroys it. In the same countries, the custom of eating raw fish further increases the potential for deficiency.

Beriberi has been described in patients with GI diseases that include malnutrition, malabsorption syndromes (eg, HIV-related enteropathy), and hyperemesis gravidarum. It has also been reported in hypermetabolic conditions such as lymphoma.

Symptoms
//Thiamine deficiency has a wide range of clinical presentations. Although clinical overlap is common, the basic phenotypes are as follows://

__Wet beriberi__ This phenotype affects the cardiovascular system and is divided into acute and chronic forms
 * In acute wet beriberi or Shoshin beriberi, the predominant injury is to the heart, and rapid deterioration occurs because of the heart's inability to maintain function.
 * Presenting symptoms include tachycardia, low diastolic pressure, cardiomegaly, pulmonary edema, and cyanosis. Wet beriberi is characterized by elevated lactic acid levels. This condition can be readily reversed with thiamine infusion, if administered early.
 * Chronic wet beriberi with high-output cardiac failure has 3 stages.
 * Initially, peripheral vasodilatation occurs, yielding high-output cardiac failure.
 * Then, the progression of vasodilatation is perceived by the kidney as a relative loss of volume. The ensuing activation of the renin angiotensin system produces greater salt and water retention.
 * Consequently, further fluid overload results in peripheral edema and pulmonary effusions.
 * Cardiac overuse injury that occurs in the above setting results in tachycardia, hypertension, and chest pain.
 * Thyrotoxicosis, a more common cause of high-output cardiac failure, is always among the differential diagnoses.

__Dry beriberi__ This phenotype affects the neuromuscular system.
 * Polyneuritis and symmetric, ascending paralysis of the peripheral nerve systems predominate.
 * The sensory system is affected first, followed by the motor and autonomic systems.
 * Typically, tactile sensation is the first to be lost, followed by pain, and, finally, temperature.
 * Paresthesia and hyperesthesia usually begin with the lower extremities and gradually involve the upper extremities and perioral area.
 * Deep tendon reflexes are lost, calf muscles become painful, and foot drop and, eventually, wrist drop occur.
 * If untreated, progressive weakness, wasting of muscles, and, ultimately, complete paralysis occur.
 * Encephalopathy is an alternative mode of presentation, with vomiting, disorientation, horizontal nystagmus, palsies of the eye movements (ophthalmoplegia), ataxia, and progressive mental impairment.
 * Korsakoff syndrome is a more ominous condition that usually precludes complete recovery. Confusion is followed by the loss of recent memory and confabulation, which is the creation of accounts of events to cover up the loss of memory.

How to Treat

 * Monitor patients with cardiac failure in an intensive care unit.
 * Because beriberi often presents with other vitamin B deficiencies, administer a complete vitamin B complex.
 * After the high-output state has been addressed with thiamine, patients can go into standard congestive heart failure and, thus, may require ongoing cardiology consultation, possibly remaining in an intensive care unit.

Other advice

 * Patients with lethargy, confusion, and severe heart failure need to be kept on a diet of nothing by mouth (NPO) to prevent aspiration.
 * Dietary sources of thiamine must be emphasized along with ongoing supplementation.
 * Patients who present with congestive heart failure should have activity restricted.

Additional Resources
[|Medscape - Overview]