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