Fat- and water-soluble vitamins, cofactors, and their deficiency syndromes tested on USMLE Step 1.
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- Which vitamin deficiency classically causes night blindness (nyctalopia)?
- Vitamin A
- What is the active form of vitamin A found in the retina that combines with opsin to form rhodopsin?
- 11-cis-retinal
- Chronic vitamin A toxicity can cause which type of intracranial condition?
- Pseudotumor cerebri (idiopathic intracranial hypertension)
- Thiamine (vitamin B1)
- Thiamine pyrophosphate (TPP), its active coenzyme form
- Name the four enzymes for which thiamine pyrophosphate (TPP) is a required cofactor.
- Pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, transketolase, and branched-chain ketoacid dehydrogenase
- In Wernicke encephalopathy, thiamine deficiency classically causes a triad of confusion, ophthalmoplegia, and ____.
- ataxia
- What are the hallmark features of Korsakoff syndrome?
- Confabulation and anterograde/retrograde memory loss
- Wet beriberi primarily affects which organ system, and dry beriberi affects which?
- Wet beriberi affects the cardiovascular system (high-output heart failure); dry beriberi affects the nervous system (peripheral neuropathy)
- Why should thiamine be given before glucose in a malnourished or alcoholic patient?
- Glucose infusion can precipitate acute Wernicke encephalopathy by depleting remaining thiamine stores
- What are the two active coenzyme forms of riboflavin (vitamin B2)?
- FAD and FMN
- What are two classic signs of riboflavin (B2) deficiency?
- Cheilosis (cracking at mouth corners) and corneal vascularization
- What are the two active coenzyme forms of niacin (vitamin B3)?
- NAD+ and NADP+
- Niacin can be endogenously synthesized from which essential amino acid?
- Tryptophan
- Pellagra, caused by niacin deficiency, presents with the classic triad of diarrhea, dermatitis, and ____.
- dementia
- Hartnup disease impairs intestinal and renal absorption of which class of amino acids, leading to pellagra-like symptoms?
- Neutral amino acids (including tryptophan)