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GTS HEMONC - b12 deficiency Flashcards

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3983481228pernicious anemia- characterized by gastric atrophy, megaloblastic anemia, neurologic degeneration (demyelination of posterior column)0
3983493456pernicious anemia- anemia sx (fatigue, DOE, pallor) - peripheral neuropathy (parethesias, numbness) - dyspepsia1
3983499416pernicious anemialaboratory exam - blood smear and bone marrow (megaloblastic maturation -- synchronization of chromatin packing and cytoplasmic maturation) - hemolysis (hyperbilirubinemia, LDH) - thrombocytopenia, leukopenia - elevated gastric pH2
3983523032hemolysis (hyperbilirubinema, LDH), thrombocytopenia, leukopenia, elevated gastric pH- pernicious anemia lab exam3
3983527973vitamin b12- cobalamin - synthesized only by microorganisms - dietary sources (liver, glands, muscle, eggs)4
39835365382-5mg- body stores of b12 - liver stores most5
39835388742-5ug- daily needs of b12 - 0.1% of stores - excreted in bile, extensive reabsorption via enterohepatic circulation6
3983549806terminal ileum- only place you can absorb b127
3983551296TCII- takes Cbl from IF in small intestine and carries Cbl from terminal ileum through blood to tissue8
3983562244methyl transfer, hydrogen transfer- 2 b12 reactions9
3983564469methyl transfer- methylation of homocystein to generate methionine - b12 is cofactor, accel rxn - methyltetrahydrofolate supplies the methyl group (substrate) - THF req for thymine and purine generation (crucial for rapidly dividing tissues)10
3983573354hydrogen transfer- generation of succinyl coA from methylmalonyl coA - crucial for myelin maintenance11
3983586474malabsorption- most common b12 deficiency - acquired12
3983597961malabsorption b12 deficiency- salivary gland dysfunction - loss of gastric function resulting in intrinsic factor deficiency/loss of gastric acid secretion - pancreatic disease - terminal ileum disease (sprue, IBD)13
3983615291autoimmune, atrophic gastritis (h. pylori), gastrectomy, aging, H2 blockers- causes loss of gastric function - causes malabsorption b12 deficiency14
3983623968acquired b12 deficiency- inadequate ingestion (vegans, brest-fed infants of vegans, breast-fed infants of deficient mothers)15
3983632865congenital b12 deficiency- transcobalamin II deficiency - Imerslund-Grasbeck syndrome16
3983637090Imerslund-Grasbeck syndrome- mutation of receptor for IF-b12 - causes congenital b12 deficiency17
3983654587low serum b12 levels (<200pg/ml), PNS/CNS disease, methylmalonic acidemia- clinical findings specific to a deficiency of vitamin b1218
3983666308falsely normal serum b12- caused by intestinal bacterial overgrowth, liver disease, myeloid disorders - more TCI and TCI analogue compared to TCII19
3983671935falsely low serum b12- caused by pregnancy, lymphoid disorders, aging, racial differences - low TCI (no analog) and no TCII analog20
3983707775pernicious (b12) anemia- tx b12 injection monthly for life - gastrectomy - tx of bacterial overgrowth in small bowel - oral vitamin supplementation in dietary deficiency, food malabsorption21
3983717566pernicious anemia- can present with anemima w/ or w/o neurologic symptoms (30%) - can present with just neurologic presentations with mild or no anemia (30%)22
3983725812dietary methionine and folate, polymorphisms in enzymatic activity- cause of variation in presentation of PA23
3983738543folic acid- synthesized by higher plants and microorganisms - daily requirement 50ug - body stores are 5mg (deficiency takes 3-4mo) - absorbed in proximal jejunum and throughout small intestine - sources are leafy greens, asparagus, broccoli, spinach, liver, kidney, fruits, mushrooms24
3983747373proximal jejunum- location of folic acid absorption25
3983753311dietary folate- primarily methyl forms of the acid - conjugated with multiple glutamic acid residues and are heat labile - deconjugation occurs in the intestine before absorption - reduced to FH4 within intestinal cells and transported to portal circulation - FH4 is polyglutamated in tissue (resistant to hydrolysis and leakage from cell)26
3983771931otc folic acid- folic acid that does not need to be methylated27
3983775422methionine synthase- enzyme that mediates rxn with folate and b12 to convert homocysteine to methionine28
3983783536cystathionine beta synthase- enzyme that mediates homocysteine to cysteine29
3983788563methylene TH4 reductase- demethylates folate with NADPH30
3983796066folate deficiency- defect in DNA synthesis is the result of uracil misincorporation into DNA, with resulting DNA strand breaks, inducing cell cycle slowing or arrest - anemia is the result of the heavy DNA synthesis requirements of the bone marrow, although all rapidly dividing cells in the body are affected - macrocytosis31
3983808057macrocyctosis of folate deficiency- asynchronous maturation of nucleus vs cytoplasm - retarded DNA synthesis (missing divisions) - retarded maturation, accommodation of MCHC32
3984123961folate deficiency- megaloblastic anemia identical to that produced by b12 deficiency33
3984141775folate deficiency- dietary deficiency state usually in a setting of general malnutrition, so other vitamin deficiencies may be present34
3984149616folate deficiency- causes neither combined system disease nor specific neuropathy35
3984151932inadequate ingestion, inadequate absorption, metabolic block in utilization, increased requirement)- causes of folate deficiency36
3984160006folate deficiency (causes)causes - inadequate ingestion (poor diet, chronic alcoholism, scurvy) - inadequate absorption (celiac disease, IBD; drugs - dilantin, barbiturates) - metabolic block in utilization (DHF reductase inhibitors, b12 loss) - increased requirement (pregnancy, infancy, hemolytic anemia)37
3984180900folate deficiencydiagnosis - serum levels < 3ng/ml (reflect recent levels) - red cell levels less than 135ng/ml (reflect chronic status)38
3984199643hyperhomocyteinemia (causes)causes - cystathionine beta synthase --> >200mmol/L - b12 deficiency --> 20-241 - folate deficiency --> 15-50 - renal disease --> 17-20 - MTHFR gene polymorphisms --> 8-15 - normal --> 4-1239
3984219128folate deficiency- deficiency associated with fetal neural tube defects - take 400ug during pregnancy (140ug/day for childbearing age)40
3984239878yes, yesmegalobastic anemia in b12, folate?41
3984242434yes, nocombined system degeneration in b12, folate?42
3984242435rare, commonpoor diet associated with b12, folate deficiency?43
3984244998no, yesother dietary deficiencies present in b12, folate?44
3984248245yes, yesinduces increase homocysteine in b12, folate?45
3984254417yes, nointrinsic factor required in b12, folate?46
3984256697yes, noassociation with increase methylmalonic in b12, folate?47

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