Beriberi overview

# Overview
Beriberi is a dietary-deficiency disease caused by a lack of thiamine in the diet. Thiamine, initially named "the anti-beriberi factor" in 1926 was the first B vitamin to be identified and is therefore referred to as vitamin B1. Thiamine is soluble in water and partly soluble in alcohol. It consists of a pyrimidine and a thiazole moiety, both of which are essential for its activity. Thiamine functions in the decarboxylation of -ketoacids, such as pyruvate -ketoglutarate, and branched-chain amino acids and thus is a source of energy generation. In addition, thiamine pyrophosphate acts as a coenzyme for a transketolase reaction that mediates the conversion of hexose and pentose phosphates.

# Historical Perspective
The word "Beriberi" is derived from the Sinhalese language, meaning "I cannot, I cannot". It used to be quite common, especially in East Asia in the 19th century. Two scientists (Dr Christiaan eijkman and Sir Frederick Hopkins) attributed beriberi to thiamine deficiency and were awarded the Nobel prize in 1929.

# Classification
Beriberi is usually classified into two types based on the main system affected (Wet and dry). The two forms may appear in the same patient, but one form dominates the disease phenotype. Other forms as infantile beriberi or Wernicke-Korsakoff syndrome occur in special populations.

# Pathophysiology
The lack of thiamine pyrophosphate (TTP) impairs the functions of four enzymes involved in energy production and neurotransmitter synthesis, namely pyruvate dehydrogenase, -ketoglutarate dehydrogenase, transketolase, and branched-chain -ketoacid dehydrogenase. Energy deprivation and deficient neurotransmitter synthesis probably explain the neural and cardiac dysfunctions, observed with beriberi.

# Causes
Thiamine deficiency can generally result from inadequate intake (as with anorexia or alcoholism), increased losses (as with excessive vomiting), and inadequate absorption (as after bariatric surgeries)

# Differentiating Beriberi overview from Other Diseases
Beriberi should be differentiated from other causes of cardiac dysfunction (wet beriberi), peripheral neuropathy (dry beriberi), delirium (WKS), and other disorders caused by excessive alcohol drinking. However, the differential diagnosis is broad due to the non-specific symptoms of cardiac and neural involvement associated with the condition.

# Epidemiology and Demographics
No clear data are available on the incidence and prevalence of beriberi; however, it is generally more common in countries with excess white rice consumption and unbalanced food supply.

# Risk Factors
The most common risk factors is consumption of diet deficient in thiamine as white rice, as well as alcoholism and being born to thiamine-deficient mothers. Other less common risk factors include inherited genetic mutations and undergoing bariatric surgery.

# Screening
There is insufficient evidence to recommend routine screening for beriberi.

# Natural History, Complications, and Prognosis

## Natural History
In infants born to thiamine-deficient mothers, the symptoms may start as early as one month of age. The hepatic stores of thiamine last for only 18 days. Lack or deficient consumption leads to gradual appearance of manifestations.

## Complications
Complications for beriberi include cachexia, heart failure, limb paralysis, delirium, and psychosis.

## Prognosis
Beriberi is an easily treatable condition with rapid improvements on thiamine administration. However, Wernicke-Korsakoff syndrome is largely irreversible and has a poor prognosis. If untreated, children with infantile Beriberi may die shortly or develop long-term motor function abnormalities.

# Diagnosis

## Diagnostic Study of Choice
Monitoring the patient's response after thiamine administration is the most cost-effective diagnostic study. A positive response is recorded if the patients clinical condition or cardiac function improved following thiamine administration.

## History and Symptoms
The symptoms of beriberi are usually vague and therefore, the diagnosis must be considered in the clinical and geographical contexts. Common symptoms for wet beriberi include tachycardia, respiratory distress, and edema, while common symptoms for dry beriberi include parasthesia, muscle pain, weakness.

## Physical Examination
There are no specific signs for Beriberi. Therefore, it should be suspected in light of the patient's symptoms and clinical setting. However, in advanced stages, the signs of cardiac dysfunction (wet beriberi) or peripheral neuropathy (dry beriberi) may be present.

## Laboratory Findings
The diagnosis of beriberi is assisted by a dietary history suggestive of a low thiamine intake and clinical manifestations. The most sensitive lab tests to detect thiamine deficiency are measurements of  erythrocyte transketolase activity (ETKA) and the thiamine pyrophosphate effect (TPPE). Other tests include measurements of urinary concentrations of thiamine and its metabolites, as well as methylglyoxal.

## Imaging Findings
There are no x-ray findings associated with beriberi.However, in advanced wet beriberi, the X-ray picture of heart failure may appear, including chamber enlargement, pleural effusion, and increased vascular markings. There are no CT scan findings associated with Beriberi. Even in Wernicke-Korsakoff syndrome, the CT scan is usually normal.In Wernicke-Korsakoff Syndrome patients, MRI may show some changes, including atrophy of mamillary bodies and hyperintense signals in the mesial dorsal thalami and periaqueductal grey matter.

## Other Diagnostic Studies
There are no other diagnostic studies associated with Beriberi.

# Treatment

## Medical Therapy
Beriberi is an easily treatable condition, using thiamine hydrochloride via oral or parentral routes. A rapid and dramatic recovery within hours can be made when this is administered to patients with beriberi.

## Surgery
Surgical intervention is not recommended for the management of Beriberi.

## Prevention
The most important preventive measure against Beriberi is increasing thiamine intake in diet. Other measures include reducing alcohol consumption and proper prenatal care of women in susceptible geographical areas.