ESSENTIALS OF DIAGNOSIS
Most common in patients with chronic alcoholism.
Early symptoms of anorexia, muscle cramps, paresthesias, irritability.
Advanced syndromes of high-output heart failure (“wet beriberi”), peripheral nerve disorders, and Wernicke-Korsakoff syndrome (“dry beriberi”).
Most thiamine deficiency in the United States is due to chronic alcoholism, with poor dietary intake of thiamine and impaired thiamine absorption, metabolism, and storage. Thiamine deficiency is also associated with malabsorption, dialysis, and other causes of chronic protein–calorie undernutrition. Thiamine deficiency can be precipitated in patients with marginal thiamine status given intravenous dextrose solutions.
Early manifestations of thiamine deficiency include anorexia, muscle cramps, paresthesias, and irritability. Advanced deficiency primarily affects the cardiovascular system (“wet beriberi”) or the nervous system (“dry beriberi”). Wet beriberi occurs in thiamine deficiency accompanied by severe physical exertion and high carbohydrate intake. Dry beriberi occurs in thiamine deficiency accompanied by inactivity and low-calorie intake.
Wet beriberi is characterized by marked peripheral vasodilation resulting in high-output heart failure with dyspnea, tachycardia, cardiomegaly, pulmonary edema, and peripheral edema with warm extremities mimicking cellulitis.
Dry beriberi involves both the peripheral and the central nervous systems. Peripheral nerve involvement is typically a symmetric motor and sensory neuropathy with pain, paresthesias, and loss of reflexes. The legs are affected more than the arms. Central nervous system involvement results in Wernicke-Korsakoff syndrome. Wernicke encephalopathy consists of nystagmus progressing to ophthalmoplegia, truncal ataxia, and confusion. Korsakoff syndrome includes amnesia, confabulation, and impaired learning.
In most instances, the clinical response to empiric thiamine therapy is used to support a diagnosis of thiamine deficiency. The most commonly used biochemical tests measure thiamine concentration directly, while other assays measure erythrocyte transketolase activity and urinary thiamine excretion. Normal thiamine values typically range from 70 nmol/L to 180 nmol/L. A transketolase activity coefficient greater than 15–20% also suggests thiamine deficiency.
Thiamine deficiency is treated with large parenteral doses of thiamine. Fifty to 100 mg/day is administered intravenously for the first few days, followed by daily oral doses of 5–10 mg/day. All patients should simultaneously receive therapeutic doses of other water-soluble vitamins. Although treatment results in complete resolution in half of patients (one-fourth immediately and another one-fourth over days), the other half obtain only partial resolution or no benefit.
Patients with signs of dry beriberi or Wernicke-Korsakoff syndrome should be referred to a neurologist. Patients with signs of wet beriberi should be referred to a cardiologist.