Wednesday, February 21, 2018

Thiamine and Beri-Beri: A Summary

  • Vitamin B1 is Thiamine.

(TCA = TriCarboxylic Acid cycle aka Kreb's cycle ; LDH = Lactate Dehydrogenase ; PDH = Pyruvate Dehydrogenase ; TPP = Thiamine PyroPhosphate)
  • Peripheral neuropathy in dry beri-beri is symmetric, sensorimotor, distal > proximal and non-inflammatory demyelinating type.
  • Wernicke's syndrome is reversible early while Korsakoff psychosis is reversible in only 20% cases.
  • Wernicke-Korsakoff syndrome has typical damage to dorsomedial nucleus of thalamus and mamillary bodies.
  • Clinical manifestations of B1 deficiency is worsened by glucose load! As seen in pathophysiology, excess of glucose with relative or absolute deficiency of B1 - as TPP - causes diversion from the preferred PDH pathway (linked to TCA), to the LDH pathway causing life-threatening lactic acidosis. Hence, in a patient with alcohol intoxication/ chronic alcoholism a B1+glucose cocktail is given as they usually are deficient in B1.
Biochemistry pearl: Other co-factors in PDH pathway alongside TPP are Lipoic acid, Coenzyme A, FAD(H) and NAD(H).


Clinical diagnosis with confirmatory lab work - that includes:
  • Diagnostic - Blood or RBC transketolase activity and increase after intramuscular B1 administration
  • Supportive - Blood thiamine, pyruvate and lactate levels

You give what the patient lacks. An acceptable regimen is:

Injection B1 100 mg intramuscular for 1 week
followed by
Tablet B1 10 mg once-daily per-oral for 1 month.

Let me know if anything needs clarification. Happy studying!
--Ashish Singh.

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