Notes in 47) Vitamin B12 Deficiency

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Published	06/12/2025	1) What key cell abnormality on a peripheral smear is classically associated with vitamin B12 deficiency?
Published	06/12/2025	2) Why does vitamin B12 deficiency cause macrocytic (megaloblastic) anemia?
Published	06/12/2025	3) Which vitamin deficiency is known to cause neurologic complications (e.g. subacute combined degeneration) — folate or vitamin B12?
Published	06/12/2025	4) Vitamin B12 is exclusively synthesized by what type of organism in nature?
Published	06/12/2025	5) Why do strict vegans risk vitamin B12 deficiency over time?
Published	06/12/2025	6) How long do typical liver stores of vitamin B12 last before deficiency appears?
Published	06/12/2025	7) Name the gastric glycoprotein crucial for vitamin B12 absorption in the terminal ileum.
Published	06/12/2025	8) What does a high serum methylmalonic acid (MMA) level specifically indicate?
Published	06/12/2025	9) Which two key enzymes in the human body require vitamin B12 as a cofactor?
Published	06/12/2025	10) What is the main difference in lab findings between folate and vitamin B12 deficiency?
Published	06/12/2025	11) Why can high-dose oral vitamin B12 sometimes treat pernicious anemia effectively?
Published	06/12/2025	12) What happens to homocysteine levels in vitamin B12 deficiency?
Published	06/12/2025	13) Explain the 'folate trap' in vitamin B12 deficiency.
Published	06/12/2025	14) Why is it dangerous to treat macrocytic anemia with folate before checking B12?
Published	06/12/2025	15) Which spinal cord tracts are primarily affected in subacute combined degeneration due to B12 deficiency?
Published	06/12/2025	16) Name a common cause of vitamin B12 deficiency in older adults characterized by autoimmune destruction of gastric parietal cells.
Published	06/12/2025	17) What classic triad is often taught for vitamin B12 deficiency?
Published	06/12/2025	18) Which medication, commonly used in diabetes, can impair B12 absorption and potentially cause deficiency?
Published	06/12/2025	19) Which type of anemia results from vitamin B12 deficiency — microcytic, normocytic, or macrocytic?
Published	06/12/2025	20) What visual disturbance can occasionally occur in vitamin B12 deficiency?
Published	06/12/2025	21) In B12 deficiency, why might there be mild jaundice?
Published	06/12/2025	22) Name one parasitic infection that can cause vitamin B12 deficiency by consuming B12 in the gut.
Published	06/12/2025	23) How do proton pump inhibitors (PPIs) contribute to vitamin B12 deficiency?
Published	06/12/2025	24) Is vitamin B12 deficiency more common in younger or older individuals, and why?
Published	06/12/2025	25) What are macro-ovalocytes on a peripheral smear?
Published	06/12/2025	26) Which lab test is highly specific for pernicious anemia but not very sensitive?
Published	06/12/2025	27) Can neurologic manifestations appear in vitamin B12 deficiency even in the absence of anemia?
Published	06/12/2025	28) What is the Schilling test historically used to diagnose?
Published	06/12/2025	29) Which RBC index typically increases above 110 fL in vitamin B12 deficiency?
Published	06/12/2025	30) Why might older patients with vitamin B12 deficiency present with 'dementia-like' symptoms?
Published	06/12/2025	31) What happens to the reticulocyte count after initiating B12 treatment in a severely deficient patient?
Published	06/12/2025	32) Explain why subacute combined degeneration affects both sensory and motor pathways.
Published	06/12/2025	33) What is the typical daily adult requirement of vitamin B12?
Published	06/12/2025	34) Which cobalamin form is longer-acting when given via injection: cyanocobalamin or hydroxocobalamin?
Published	06/12/2025	35) Why can pernicious anemia lead to increased gastric cancer risk?
Published	06/12/2025	36) What is the function of R-binder (haptocorrin) in B12 absorption?
Published	06/12/2025	37) After absorption in the terminal ileum, which protein carries vitamin B12 in the bloodstream?
Published	06/12/2025	38) Name a neurological sign that tests proprioception often lost in B12 deficiency.
Published	06/12/2025	39) Why does B12 deficiency sometimes cause mild indirect hyperbilirubinemia?
Published	06/12/2025	40) Which deficiency accumulates methylmalonic acid: vitamin B12 or folate deficiency?
Published	06/12/2025	41) What neurologic phenomenon might be found on exam if lateral corticospinal tracts are damaged?
Published	06/12/2025	42) Why might pregnant vegans be at particular risk for vitamin B12 deficiency?
Published	06/12/2025	43) How does a positive Babinski sign manifest?
Published	06/12/2025	44) Which class of medication used for GERD can lead to 'food-bound B12 malabsorption'?
Published	06/12/2025	45) Why might severe vitamin B12 deficiency lead to a combined picture of anemia plus thrombocytopenia and leukopenia?
Published	06/12/2025	46) Which chronic GI disease involving the ileum often causes B12 deficiency?
Published	06/12/2025	47) What is the best next diagnostic step if a patient has low-normal B12 (e.g., 250 pg/mL) but suspected deficiency?
Published	06/12/2025	48) Identify a classic physical finding on the tongue in severe B12 deficiency.
Published	06/12/2025	49) What is the role of acid and pepsin in B12 absorption?
Published	06/12/2025	50) Name two major autoimmune conditions commonly associated with pernicious anemia.
Published	06/12/2025	51) Does vitamin B12 have a known toxic upper limit?
Published	06/12/2025	52) Why is methylmalonic acid considered neurotoxic in B12 deficiency?
Published	06/12/2025	53) In megaloblastic anemia, what is the typical shape/size of RBCs?
Published	06/12/2025	54) Name a key reason to suspect B12 deficiency in a diabetic patient complaining of new neuropathy.
Published	06/12/2025	55) Which factor must be present in the terminal ileum for B12 absorption via receptor-mediated endocytosis?
Published	06/12/2025	56) How quickly can an exclusively breastfed infant of a B12-deficient mother become deficient?
Published	06/12/2025	57) What is one reason B12 deficiency can lead to elevated homocysteine levels?
Published	06/12/2025	58) Which B12 deficiency etiology involves intestinal bacteria overgrowing and using up the vitamin?
Published	06/12/2025	59) What is the classic RBC appearance in pernicious anemia?
Published	06/12/2025	60) What might trigger acute neurologic deterioration in a patient with marginal B12 stores who receives nitrous oxide?
Published	06/12/2025	61) What are two forms of active vitamin B12 in the body?
Published	06/12/2025	62) Why is atrophic gastritis in pernicious anemia clinically relevant besides causing B12 deficiency?
Published	06/12/2025	63) Name a test you might perform if you suspect an autoimmune etiology for B12 deficiency but anti-IF antibody is negative.
Published	06/12/2025	64) Which lab finding can differentiate copper deficiency myelopathy from B12 deficiency myelopathy?
Published	06/12/2025	65) Why do RBCs become macrocytic when B12 is lacking?
Published	06/12/2025	66) What are some common neurologic manifestations of B12 deficiency?
Published	06/12/2025	67) Why might numbness in the feet be the earliest neuropathic sign in B12 deficiency?
Published	06/12/2025	68) How does vitamin B12 deficiency affect the reticulocyte count?
Published	06/12/2025	69) When do you typically see a reticulocyte 'surge' after initiating B12 therapy?
Published	06/12/2025	70) Why is it important to check for pernicious anemia in a newly diagnosed B12-deficient patient?
Published	06/12/2025	71) Name an endocrine disorder that may coexist with pernicious anemia due to autoimmune clustering.
Published	06/12/2025	72) What happens to the RBC distribution width (RDW) in megaloblastic anemias?
Published	06/12/2025	73) How does B12 deficiency potentially cause neuropsychiatric changes like depression or irritability?
Published	06/12/2025	74) Can vitamin B12 deficiency present solely with cognitive impairment (e.g., dementia) in some patients?
Published	06/12/2025	75) Why might patients with B12 deficiency have an elevated LDH level?
Published	06/12/2025	76) What is the typical appearance of neutrophils in megaloblastic anemia?
Published	06/12/2025	77) Name two reasons that cause vitamin B12 to get 'trapped' in the gut lumen, leading to deficiency.
Published	06/12/2025	78) Does folate supplementation help correct elevated methylmalonic acid in B12 deficiency?
Published	06/12/2025	79) What specific type of dorsal column sensation is commonly lost first in B12 deficiency?
Published	06/12/2025	80) Name one recommended prophylactic measure for patients who have undergone gastric bypass surgery.
Published	06/12/2025	81) How does high-dose oral vitamin B12 therapy overcome malabsorption in pernicious anemia?
Published	06/12/2025	82) When suspecting B12 deficiency, why do we check serum folate as well?
Published	06/12/2025	83) Explain why you might see a mild elevation in unconjugated bilirubin in B12 deficiency.
Published	06/12/2025	84) In diagnosing B12 deficiency, which test is more definitive when levels are borderline: MMA or homocysteine alone?
Published	06/12/2025	85) Which populations should be screened periodically for B12 deficiency?
Published	06/12/2025	86) Why is 'pancytopenia' possible in vitamin B12 deficiency?
Published	06/12/2025	87) Describe the phenomenon of 'subacute' in subacute combined degeneration.
Published	06/12/2025	88) Is the Schilling test commonly performed in modern clinical practice?
Published	06/12/2025	89) Which important cofactor is regenerated from 5-methyltetrahydrofolate when B12 is present?
Published	06/12/2025	90) Why can an older patient with borderline B12 levels still exhibit severe deficiency symptoms?
Published	06/12/2025	91) In pernicious anemia, what are two antibody targets?
Published	06/12/2025	92) Which nutrition deficiency can mimic B12 neurologically yet has normal MMA and often presents with hemolysis?
Published	06/12/2025	93) Why should you consider checking copper levels in a patient who doesn’t respond to B12 therapy?
Published	06/12/2025	94) What is the typical time frame for full hematologic correction (normal Hgb) after starting B12 therapy?
Published	06/12/2025	95) Name one risk factor for small intestinal bacterial overgrowth that can lead to B12 deficiency.
Published	06/12/2025	96) How does the body normally 'recycle' B12 after excretion in bile?
Published	06/12/2025	97) A patient on chronic nitrous oxide for analgesia develops paresthesias: suspect what deficiency?
Published	06/12/2025	98) Which condition is associated with megaloblastic anemia and 'beefy red tongue'?
Published	06/12/2025	99) In B12 deficiency, is RBC destruction mostly extravascular or intramedullary?
Published	06/12/2025	100) Name a cause of B12 deficiency where the acidic environment isn’t sufficient to release B12 from food proteins.
Published	06/12/2025	101) How soon can neurological symptoms become partly irreversible in vitamin B12 deficiency?
Published	06/12/2025	102) What is the significance of 'cubilin' in vitamin B12 absorption?
Published	06/12/2025	103) Why might total gastrectomy immediately predispose to B12 deficiency?
Published	06/12/2025	104) If a patient has combined folate and B12 deficiencies, which should be replaced first?
Published	06/12/2025	105) Which food sources are the most concentrated in natural vitamin B12?
Published	06/12/2025	106) How can long-term heavy alcohol use contribute to B12 deficiency?
Published	06/12/2025	107) Why is spastic weakness a sign of lateral corticospinal tract involvement?
Published	06/12/2025	108) What does 'megaloblastic madness' refer to?
Published	06/12/2025	109) Which form of B12 replacement might be given monthly via injection?
Published	06/12/2025	110) Why does the body need vitamin B12 to generate S-adenosylmethionine (SAM)?
Published	06/12/2025	111) What might you suspect if a patient has RBC macrocytosis but no hypersegmented neutrophils?
Published	06/12/2025	112) How is the positivity of a Romberg test interpreted in B12 deficiency?
Published	06/12/2025	113) Why does pernicious anemia typically require lifelong B12 therapy?
Published	06/12/2025	114) Name one factor that can raise suspicion for B12 deficiency in an infant.
Published	06/12/2025	115) How quickly can neurologic improvement begin after starting B12 repletion in a deficient patient?
Published	06/12/2025	116) Why should you check TSH in a patient with new pernicious anemia?
Published	06/12/2025	117) How do RBCs appear under the microscope in megaloblastic anemia besides being large?
Published	06/12/2025	118) What is a dangerously low B12 level considered by most labs?
Published	06/12/2025	119) Which anemia is corrected by folate supplementation but still leaves neurologic deficits untreated?
Published	06/12/2025	120) Describe the typical gait changes in subacute combined degeneration.
Published	06/12/2025	121) Name a reason excessive zinc intake can cause a B12-like neurologic picture.
Published	06/12/2025	122) What is meant by 'intrinsic factor blocking antibody'?
Published	06/12/2025	123) Why might someone with advanced HIV have B12 deficiency?
Published	06/12/2025	124) Which test can confirm an autoimmune gastric atrophy in pernicious anemia?
Published	06/12/2025	125) What commonly used diabetes medication is recommended to be monitored for B12 deficiency after prolonged use?
Published	06/12/2025	126) Why can high-output heart failure occur in severe untreated megaloblastic anemia?
Published	06/12/2025	127) A 70-year-old on a PPI for years has mild memory loss and fatigue. Which deficiency should you suspect?
Published	06/12/2025	128) Describe the relationship between B12 deficiency and 'psychosis' sometimes termed megaloblastic madness.
Published	06/12/2025	129) If you see macrocytosis (MCV ~110) with normal B12 and folate, name a hematologic condition to consider.
Published	06/12/2025	130) In B12 deficiency, a 'beefy red tongue' is also known as what?
Published	06/12/2025	131) What is the main difference in RBC precursor appearance in the bone marrow in megaloblastic anemia?
Published	06/12/2025	132) Which B12 transport protein deficiency presents early in life with severe megaloblastic anemia?
Published	06/12/2025	133) Give an example of a neuro exam finding that suggests combined dorsal column and corticospinal tract disease.
Published	06/12/2025	134) Why might an elevated serum gastrin level be found in pernicious anemia?
Published	06/12/2025	135) Why can a patient’s RBCs still be macrocytic if iron deficiency coexists with B12 deficiency?
Published	06/12/2025	136) Name one reason to suspect B12 deficiency in a patient complaining of frequent falling in dim light.
Published	06/12/2025	137) Which organ contains the majority of stored vitamin B12?
Published	06/12/2025	138) Why is checking serum MMA especially important in patients with borderline-low B12 levels?
Published	06/12/2025	139) Which nutritional deficiency might appear within a few months: folate or vitamin B12?
Published	06/12/2025	140) If a patient’s neuro symptoms worsen despite normalizing hemoglobin after folate therapy, what was likely missed?
Published	06/12/2025	141) Name two recommended administration routes for vitamin B12 replacement.
Published	06/12/2025	142) Which RBC index often goes back to normal last during B12 repletion: Hemoglobin or MCV?
Published	06/12/2025	143) What is an example of a postpartum complication if the mother is B12-deficient?
Published	06/12/2025	144) State a potential complication of giving packed RBC transfusions to a severely B12-deficient patient.
Published	06/12/2025	145) How does megaloblastic anemia differ from aplastic anemia in terms of marrow cellularity?
Published	06/12/2025	146) Why might a patient’s neuropathy not fully resolve if B12 deficiency is treated late?
Published	06/12/2025	147) Explain how B12 deficiency might contribute to elevated cardiovascular risk.
Published	06/12/2025	148) Which relatively rare condition can cause B12 deficiency due to an inherited receptor defect in the terminal ileum?
Published	06/12/2025	149) If a patient has megaloblastic anemia and normal B12, normal folate, but neurological symptoms, what should you suspect?
Published	06/12/2025	150) Why is it best to monitor serum potassium levels when starting B12 therapy in a severely anemic patient?
Published	06/12/2025	151) What is the recommended initial frequency of IM B12 injections for severe deficiency?
Published	06/12/2025	152) How does elevated homocysteine help differentiate megaloblastic anemia from other macrocytoses?
Published	06/12/2025	153) Why is the neurological syndrome in B12 deficiency called 'combined'?
Published	06/12/2025	154) When using oral high-dose B12 therapy, which approximate daily dose is often recommended?
Published	06/12/2025	155) Why might a patient with advanced liver disease show abnormal B12 levels?
Published	06/12/2025	156) Name one reason an alcoholic might have borderline B12 levels but still be clinically deficient.
Published	06/12/2025	157) How can you tell megaloblastic macro-ovalocytes from macrocytosis due to alcohol alone?
Published	06/12/2025	158) Is B12 deficiency more likely in a 2-year vegan or a 10-year vegan?
Published	06/12/2025	159) Name an advanced neurological complication of untreated B12 deficiency affecting sphincters.
Published	06/12/2025	160) Why is it said that 'vitamin B12 deficiency can be a great masquerader'?
Published	06/12/2025	161) How do you confirm suspicion of pernicious anemia once B12 deficiency is established?
Published	06/12/2025	162) In which form is pharmaceutical B12 often provided for injections?
Published	06/12/2025	163) Why might borderline B12 levels with normal MMA not warrant immediate B12 supplementation?
Published	06/12/2025	164) Name one reason older adults with B12 deficiency may lack classic GI symptoms.
Published	06/12/2025	165) How quickly do neurological symptoms sometimes improve if they’ve been present <6 months?
Published	06/12/2025	166) What is the rationale for giving prophylactic B12 injections to post–gastrectomy patients?
Published	06/12/2025	167) In the differential diagnosis of macrocytic anemia, what single lab test can immediately suggest megaloblastic etiology?
Published	06/12/2025	168) How can B12 deficiency cause irritability or mood changes?
Published	06/12/2025	169) What is the typical normal range for serum B12 in pg/mL in most labs?
Published	06/12/2025	170) Summarize the most important clinical pearl regarding B12 and folate interplay.
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