Vitamin B1 (thiamine) deficiency

Vitamin B1 (thiamine) deficiency

Definition

Deficiency of thiamine (vitamin B1).

Aetiology

Insufficient intake of thiamine, which is present in for-tified wheat flour (the natural thiamine is removed by milling, so it is replaced in most countries), fortified breakfast cereals, milk, eggs, yeast extract and fruit. Alcoholics are most commonly affected in the United Kingdom, because of malnutrition.

Pathophysiology

Thiamine is an essential factor for the maintenance of the peripheral nervous system and the heart. It is also involved in glycolytic pathways, mediating carbohydrate metabolism.

Clinical features

Dry beriberi is an endemic form of polyneuritis resulting from a diet consisting of polished rice deficient in thiamine. The neuropathy predominantly affects the legs with weakness, parasthesia and loss of ankle jerks. Cerebral involvement causes Wernicke–Korsakoff ’s syndrome. Wet beriberi is the high output heart failure caused by thiamine deficiency resulting in oedema. Wet beriberi is rare in alcoholics.

Investigations

Diagnosis is usually clinical and on response to thiamine. Erythrocyte transketolase activity and blood pyruvate are increased.

Management

Thiamine is replaced orally, intravenously or intramuscularly. The cardiac failure usually responds rapidly, but neuropathies may only partially resolve if they are long-standing.