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Syn: Beri-Beri
Thiamine was actually the active ingredient in the
original description of vitamin B, which was defined as a water-soluble
extract in rice polishings that cured beri-beri (clinical thiamine
deficiency).
This disease was classically seen in the
Orient, where the
staple food was polished rice that had been deprived of its thiamine
content by processing.
Vitamins : click
With increased awareness of the disease and
improved nutrition in some areas, this disorder is less common now than in
previous generations.
Thiamine deficiency in humans affects the cardiovascular, muscular,
nervous, and gastrointestinal systems.
Nutritional
Pathology Online : click
The cardinal symptoms of thiamine deficiency are
polyneuropathy, edema, and cardiac failure.
The deficiency syndrome is
classically divided into dry beri-beri, with symptoms referable to
the neuromuscular system, and wet beri-beri, in which the symptoms
of cardiac failure predominate.
Patients with dry beri-beri presents with
paresthesias, depressed reflexes, and weakness and atrophy of the muscles
of the extremities.
Wet beri-beri is characterized by generalized edema, a
reflection of severe congestive failure.
The basic lesion is an
uncontrolled, generalized vasodilatation and significant peripheral arteriovenous
shunting.
This combination leads to a compensatory increase in cardiac output, and
eventually to a large dilated heart and congestive heart failure.
In the absence of a documented metabolic disease (e.g., hyperthyroidism),
high output failure and generalized edema are strongly suggestive of
thiamine deficiency.
Thiamine deficiency in chronic alcoholics may be
manifested by involvement of the brain in the form of Wernicke's
syndrome, in which progressive dementia, ataxia, and ophthalmoplegia (paralysis of the extraocular muscles) are prominent.
Korsakoff's
syndrome, in which a thought disorder is conspicuous, at one time
attributed solely to thiamine deficiency, but it now appears to be a
finding both in chronic alcoholics and in patients with other organic
mental syndromes.
Pathologic examination of the nervous system in
cases of thiamine deficiency has not defined a pathognomonic change in the
peripheral nerves, since similar or identical changes can be seen in a
variety of other diseases characterized by peripheral neuropathy.
A
characteristic alteration is degeneration of myelin sheaths, often beginning
in the sciatic nerve and then involving other peripheral nerves, and
sometimes the spinal cord itself.
In the few advanced cases that have been studied, fragmentation of the
axons has been noted.
In Wernicke’s
encephalopathy the most striking lesions are found in the mammillary
bodies and surrounding areas that abut on the third ventricle.
Atrophy of the mammillary bodies can be visualized in alcoholics by
computerized tomography and magnetic resonance imaging.
Microscopically, degeneration and loss of ganglion cells, rupture of small
blood vessels, and ring hemorrhages are seen in the brain.
The changes in the heart are also nonspecific.
Grossly, the heart is flabby, dilated and increased in weight. The process
may affect either right or left side of the heart, or both.
The microscopic changes are nondescript, and include edema, inconsistent
fiber hypertrophy, and occasional foci of fiber degeneration.
At one time, all primary myocardial diseases in the alcoholic were
considered to reflect thiamine deficiency, but it is now recognized that
the large majority are unrelated to thiamine & are caused by a direct
toxic effect of alcohol (alcoholic cardiomyopathy ).
The most reliable diagnostic test for thiamine
deficiency is an immediate and dramatic response to parenteral
thiamine.
Measurements of levels of thiamine in the blood and red blood cell transketolase activity are also useful.
The biochemical basis
of the symptoms in thiamine deficiency is not understood.
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