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Heme / Onc > SM_250b: Megaloblastic Anemias > Flashcards

SM_250b: Megaloblastic Anemias Flashcards

1
Q

These are ____

A

Megaloblasts in bone marrow

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2
Q

Megaloblasts result from ___

A

Megaloblasts result from defective DNA synthesis

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3
Q

Describe consequences of megaloblastosis

A

Consequences of megaloblastosis

  • Bone marrow: ineffective erythropoiesis: hypercellular marrow, increase in bilirubin and LDH and decrease in haptoglobin because contents of cytoplasm released
  • Peripheral blood: macro-ovalocytes (increased average RBC size), neutrophil hypersegmentation
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4
Q

Megaloblastic anemia most commonly results from ____ or ____

A

Megaloblastic anemia most commonly results from Vitamin B12 deficiency or folic acid deficiency

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5
Q

Describe the intersection of B12 and folate metabolism

A

Intersection of B12 and folate metabolism

  • Vitamin B12 accepts methyl group from methyltetrahydrofolate -> methylates homocysteine to generate methionine -> provides tetrahydrofolate required for folate coenzymes that aid in purine and pyrimidine synthesis and thymidylate for DNA synthesis
  • Hydrogen transfer: generation of succinyl CoA from methylmalonyl CoA
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6
Q
A
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7
Q

Vitamin B12 deficiency leads to ___ and ___

A

Vitamin B12 deficiency leads to

  • Increase in homocysteine due to impaired methyl transfer
  • Increase in methylmalonic acid
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8
Q

Describe Vitamin B12 absorption

A

Vitamin B12 absorption: meat, eggs, dairy (3-5 ug)

  1. Gastric acid liberates B12 from binding proteins
  2. Binding to salivary HC
  3. Duodenum: pancreatic proteases release B12 from HC
  4. Intrinsic factor secreted by gastric parietal cells and binds B12
  5. IF-B12 complex bound in ileum (cubam receptor)
  6. Bound to TCII and distributed

Robust liver stores

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9
Q

Describe causes of Vitamin B12 deficiency

A

Vitamin B12 deficiency

  • Malabsorption >>> dietary deficiency
  • Gastric disease: acid poor environment, surgery, lack of intrinsic factor
  • Pancreatic disease
  • Intestinal disorders: IBD, bacterial overgrowth, celiac, malignancy
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10
Q

Pernicious anemia is ___

A

Pernicious anemia is an autoimmune illness in which autoantibodies destroy gastric parietal cells, leading to deficient HCl production

  • Antiboides that bind intrinsic factor
  • Often see in older adults
  • Can exist with other autoimmune illness
  • Association with malignancy (gastric cancer and carcinoid tumors)
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11
Q

Pernicious anemia leads to ___ and ___

A

Pernicious anemia leads to ineffective erythropoiesis and subacute combined degeneration

  • Ineffective erythropoiesis: anemia, thrombocytopenia, leukopenia, hemolysis (LDH, increased bilirubin)
  • Subacute combined degeneration: brain and cranial nerves (dementia and personality change), neuropathy (loss of vibratory and position sense, abnormal sensations of hands and feet)
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12
Q

Describe clinical and laboratory findings suggestive of Vitamin B12 deficiency

A

Vitamin B12 deficiency

  • PNS and CNS disease
  • Low serum B12 levels (< 200 pg/mL)
  • Increased methylmalonic acid
  • Increased homocysteine
  • Anti-parietal and/or intrinsic factor antibodies (serum gastrin may also be increased)
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13
Q

Describe treatment of Vitamin B12 deficiency

A

Vitamin B12 deficiency treatment

  • Underlying cause of possible
  • Intramuscular or high dose oral treatment
  • Lifelong treatment when cause unknown or irreversible
  • Therapy not always appropriate
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14
Q

Vitamin B12 clinical presentation varies from ___ to ___

A

Vitamin B12 clinical presentation varies from severe anemia without neurologic symptoms to predominantly neurologic presentations with mild/no anemia

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15
Q

Folic acid comes from ____ but the body stores ____

A

Folic acid comes from leafy green vegetables but the body stores minimal

  • Absorption in small intestine
  • Byproducts taken up by liver and can be recycled into bile for gut reabsorption (enterohepatic circulation)
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16
Q

Describe causes of folate deficiency

A

Folate deficiency causes

  • Dietary: poor diet, chronic alcoholism
  • Increased requirements: hemolytic anemia, pregnancy
  • Malabsorption (small intestinal disorders): celiac disase, IBD
  • Metabolic block in utilization: dihydrofolate reductase inhibitors (methotrexate, trimethoprim)
  • Loss: hemodialysis
17
Q

Describe clinical features of folate deficiency

A

Folate deficiency clinical features

  • Megaloblastic anemia identical to that produced by Vitamin B12 deficiency
  • Neither combined system neurologic disease nor specific neuropathy
  • Dietary deficiency state usually in setting of general malnutrition so other clinical features usually present
  • NTDs in pregnancy
18
Q

Describe diagnosis of folate deficiency

A

Folate deficiency diagnosis

  • Serum folate levels < 2 ng/mL: sensitive to recent intake, acute EtOH binge can result in low levels
  • RBC folate levels < 280 nm/L: reflects chronic folate status, can be low in Vitamin B12 deficiency
  • Elevated serum homocysteine
19
Q

Describe treatment for folate deficiency

A

Folate deficiency treatment

  • Oral folic acid: 1-5 mg daily (easily absorbed)
  • Prophylactic treatment in patients with high demand
  • Must exclude Vitamin B12 deficiency: folate supplementation can improve anemia but will not correct neurologic manifestations
20
Q

Compare Vitamin B12 and folate deficiencies

A

Vitamin B12 and folate deficiencies

21
Q

Describe other causes of macrocytosis

A

Other causes of macrocytosis (MCV > 100)

  • Alcohol
  • Liver disease
  • Hypothyroidism
  • Bone marrow failure states (aplastic anemia, myelodysplastic syndrome)
  • Reticulocytosis
  • Drugs (hydroxyurea, anti-retrovirals), artifact
22
Q

Describe clinical manifestations of copper deficiency

A

Copper deficiency

  • Macrocytic anemia (also neutropenia)
  • Bone marrow findings can mimic myelodysplastic syndromes
  • Neurologic symptoms: ataxia, neuropathy
  • Fragile hair, depigmentation
  • Edema
  • Osteoporosis
  • Risk factors: gastric bypass (absorbed in stomach and small intestine), celiac disease, excess zinc ingestion, and total parenteral nutrition
23
Q

___ is treatment for copper deficiency

A

Copper supplementation is treatment for copper deficiency

Heme / Onc (41 decks)

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