Deficiency diseases – thiamine: The neurological and cardiovascular syndrome known as Beriberi is caused by a deficiency of which vitamin?

Introduction / Context:
B-complex vitamins function as coenzymes in core metabolic pathways. Thiamine (vitamin B1) supports oxidative decarboxylation and transketolase reactions. Its deficiency produces Beriberi, with “dry” (neuropathy) and “wet” (cardiomyopathy, edema) forms, and Wernicke–Korsakoff syndrome in alcoholism.

Given Data / Assumptions:

• Identify which vitamin corresponds to Beriberi.
• Recall key enzyme complexes requiring thiamine pyrophosphate (TPP): pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, branched-chain ketoacid dehydrogenase, and transketolase.
• Consider clinical features tied to energy deficiency in nervous and cardiac tissues.

Concept / Approach:
Thiamine deficiency impairs ATP production from carbohydrates due to blocked entry of pyruvate into the TCA cycle and reduced pentose phosphate flux. High-energy tissues (nerves, heart) manifest symptoms first. Treatment with thiamine reverses early symptoms; in chronic cases neurological deficits may persist.

Step-by-Step Solution:
Map clinical syndrome (Beriberi) to thiamine deficiency.Exclude other vitamins: riboflavin (ariboflavinosis), pyridoxine (neuropathy, sideroblastic anemia), B12 (megaloblastic anemia with neuropathy), niacin (pellagra).Select vitamin B1 (thiamine).

Verification / Alternative check:
Response to thiamine therapy and laboratory testing (e.g., transketolase activity in RBCs) confirm diagnosis.

Why Other Options Are Wrong:

• B2: Cheilosis, glossitis; not Beriberi.
• B6: Neuropathy, dermatitis; not classic Beriberi.
• B12: Megaloblastic anemia, neurologic deficits distinct from Beriberi.
• Niacin: Pellagra (dermatitis, diarrhea, dementia).

Common Pitfalls:
Attributing neuropathy solely to B6 or B12; thiamine deficiency produces a characteristic combination including cardiomyopathy in “wet” Beriberi.

Final Answer:
vitamin B1 (thiamine).