🧠 Thiamine (Vitamin B1) Deficiency for USMLE Step 1: Enzymes, Syndromes, and Neurologic Findings

Thiamine (Vitamin B1) is essential for energy production in high-demand tissues like the brain and heart. It serves as a cofactor for several key dehydrogenase enzymes.

Step 1 loves to test:

• Which enzymes require TPP (thiamine pyrophosphate)

• The difference between Wernicke, Korsakoff, and beriberi

• The clinical impact of deficiency in alcoholic and malnourished patients

🔬 Enzymes That Require Thiamine (TPP)

Enzyme	Pathway
Pyruvate dehydrogenase (PDH)	Links glycolysis to TCA cycle
α-Ketoglutarate dehydrogenase	TCA cycle
Branched-chain ketoacid dehydrogenase	BCAA metabolism
Transketolase	HMP shunt (Pentose Phosphate Pathway)

🧠 Mnemonic:
"ATP"

• Alpha-ketoglutarate DH

• Transketolase

• Pyruvate DH
  (+ Branched-chain ketoacid DH)

🧠 Neurologic Syndromes

🟣 Wernicke Encephalopathy

• Reversible (early)

• Triad:

  • Confusion

  • Ataxia

  • Ophthalmoplegia

• Associated with alcoholism or hyperemesis

⚫ Korsakoff Syndrome

• Irreversible

• Anterograde and retrograde amnesia

• Confabulation (hallmark)

• Atrophy of mammillary bodies

💓 Cardiovascular Findings

🔵 Dry Beriberi

• Polyneuropathy

• Symmetrical muscle wasting

❤️ Wet Beriberi

• High-output cardiac failure

• Dilated cardiomyopathy

• Edema

🚨 Clinical Application: Alcoholic Patient

Syndrome	Key Features
Wernicke encephalopathy	Confusion, ataxia, ophthalmoplegia — reversible if caught early
Korsakoff syndrome	Confabulation, memory loss, irreversible damage to mammillary bodies

📚 Histology Buzzwords

Structure	Change
Mammillary bodies	Necrosis in Wernicke/Korsakoff syndrome
Brainstem nuclei	Hemorrhage, atrophy
Heart (wet beriberi)	Dilation, myocyte degeneration

🧠 Mnemonics to Remember

“B1 = Brain + 1 Heart”

• Deficiency hits CNS + cardiovascular systems

“Wernicke = What? Korsakoff = Confabulate”

“Always Treat Patients First”

• Alcohol

• Thiamine

• Pyruvate DH

• Feed later

⚠️ Step 1 Clinical Clue

A 48-year-old man with alcoholism presents with confusion, gait instability, and lateral gaze palsy. Labs show low thiamine. What is the most likely brain lesion?

✅ Answer: Wernicke encephalopathy → mammillary body damage

🎯 Call-To-Action

Want to lock in your vitamin and cofactor pathways?

🧠 Explore KOTC’s Metabolism Visual Vault + Cofactor Qbank:
🔗 https://kingofthecurve.org/trial-sessions

🎓 Or grab lifetime access to get full metabolic flowcharts and NBME-style cases:
🔗 https://kingofthecurve.org/free-lifetime

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