Thiamine Deficiency and Beriberi
On this page
Direct answer
Thiamine (vitamin B1) deficiency causes beriberi: wet beriberi produces high-output heart failure and dry beriberi produces symmetric neuropathy. Thiamine pyrophosphate is the cofactor for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and transketolase. Polished rice diets and chronic alcohol use are the classic settings, and Wernicke encephalopathy is the central nervous form of the same deficiency.
What you must remember
- Cofactor role: thiamine pyrophosphate serves pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and transketolase, so deficiency causes lactate accumulation and energy failure.
- Wet beriberi: high-output cardiac failure with tachycardia, warm vasodilated peripheries, oedema and raised venous pressure, often improving within hours to days of parenteral thiamine.
- Dry beriberi: symmetric length-dependent sensorimotor neuropathy with calf tenderness, foot drop, wasting and early loss of ankle reflexes.
- Infantile beriberi: exclusively breastfed infants of deficient mothers develop aphonia, irritability and cardiac failure in the first months of life.
- Causes: polished rice diets, alcohol use, hyperemesis, bariatric surgery, prolonged dialysis, diuretics, and high-carbohydrate loads given to a deficient patient.
- Diagnosis: serum thiamine is insensitive, and erythrocyte transketolase activity is the functional test; a therapeutic trial is often the practical diagnosis.
- Treatment: parenteral thiamine, in higher doses for Wernicke features, then oral maintenance, with thiamine given before any glucose infusion.
Worked example: a breathless drinker with a fast heart
A 58-year-old daily drinker presents with breathlessness, ankle swelling and a pulse of 120, with warm peripheries and raised venous pressure. The echocardiogram shows a dilated, hyperdynamic heart, which is not the picture of a simple failing pump.
- Narrow the differential: Lactate is raised and thyroid function is normal, so thyrotoxicosis is excluded, and wet beriberi on a background of alcohol use becomes the working diagnosis.
- Give thiamine first: Parenteral thiamine is given at once, before glucose-containing fluids and before any diuretic, since diuretics increase thiamine loss.
- Replace magnesium: Magnesium is checked and replaced, because it is needed for thiamine-dependent enzymes.
- Give fluids cautiously: A high-output heart with thiamine deficiency tolerates volume poorly.
- Look for Wernicke signs: Neurological features such as nystagmus and confusion are examined for, since they would raise the dose.
- Reassess the response: A falling heart rate and easier breathing over a day support the diagnosis, while a poor response points to alcoholic cardiomyopathy or another cause.
A second patient with burning feet and foot drop has dry beriberi. The same thiamine therapy applies, but nerve recovery takes months and physiotherapy is needed.
Where wet and dry beriberi get reversed
Beriberi questions turn on the organ affected and the order of treatment.
- Trap: Swapping wet and dry beriberi. Correct: Wet means heart and oedema, while dry means nerves and wasting, so tie the mnemonic to the organ.
- Trap: Mistaking wet beriberi for thyrotoxicosis or septic shock. Correct: Both show tachycardia and warm peripheries, so the alcohol history and a normal thyroid result point to beriberi.
- Trap: Missing the infantile form. Correct: The mother may have few symptoms, and the infant presents with aphonia, a distinctive stem clue.
- Trap: Giving glucose before thiamine. Correct: Carbohydrate metabolism uses up the remaining thiamine and can precipitate or worsen Wernicke encephalopathy.
Frequently asked questions
Which enzymes depend on thiamine pyrophosphate?
Thiamine pyrophosphate is the cofactor for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and transketolase. Deficiency of any of these causes lactate accumulation, energy failure and the neurological and cardiac features of beriberi.
What is the difference between wet and dry beriberi?
Wet beriberi causes high-output cardiac failure with oedema and warm peripheries, while dry beriberi causes symmetric peripheral neuropathy with foot drop and wasting. Both respond to parenteral thiamine, though the neuropathy recovers over months rather than hours.
Which infants are at risk of infantile beriberi?
Exclusively breastfed infants of thiamine-deficient mothers are at risk of infantile beriberi, which presents in the first months of life with aphonia, irritability and cardiac failure. Maternal thiamine status should be checked when an infant presents this way.
Why is thiamine given before glucose in deficient patients?
Thiamine is given before glucose because carbohydrate metabolism consumes thiamine that is already scarce, and the glucose load can precipitate or worsen Wernicke encephalopathy. In at-risk patients, parenteral thiamine always comes first, followed by glucose-containing fluids.
Which laboratory test best assesses thiamine status?
Erythrocyte transketolase activity is the most useful functional test of thiamine status, because serum thiamine levels are insensitive. A rise in activity after adding thiamine pyrophosphate in vitro confirms deficiency, though the test is not always available in routine practice.