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Hematology Chapter 12
Megaloblastic and Nonmegaloblastic Macrocytic Anemias
41
Biology
Graduate
11/12/2012

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Term
Cause and process of megaloblastic maturation in the bone marrow
Definition
Megaloblastic anemia is classified as a nuclear maturation defect, large degree of ineffective Erythropoiesis resulting from disrupted DNA synthesis. Megaloblasts describes any maturation stage of the megaloblastic erythroid series, bone marrow is hypercellular with megaloblastic erythroid precursors and decreased M: E ration
Term
Body’s requirements for vitamin B12 and folate and their physiologic role
Definition
Both are vitamins necessary as coenzymes for nucleic acid synthesis, B12 deficiency is secondary to an intrinsic factor deficiency (factor necessary for absorption of B12). Folic acid deficiency is due to inadequate dietary uptake
Term
Tests used to confirm a diagnosis of vitamin B12 deficiency
Definition
Measurement of increased excretion of methylmalonic acid in the urine indirectly indicated decrease in B12 levels. Homocysteine is increased in people with B12 deficiency
Term
Tests used to confirm a diagnosis of folic acid deficiency
Definition
Serum and erythrocyte folate levels must be decreased
Term
six most common disorders that result in a macrocytic anemia
Definition
(1) Alcoholism (2) liver disease (3)stimulated Erythropoiesis (4) hypothyroidism (5) B12 deficiency and (6) folate deficiency
Term
Pernicious anemia etiology
Definition
absence of IF secondary to gastric atrophy (leads to B12 deficiency)
Term
Pernicious anemia Pathophysiology
Definition
gastric atrophy is thought to result from immune destruction of the acid-secreting portions of the gastric mucosa
Term
Pernicious anemia Clinical symptoms
Definition
gastric atrophy, achlorhydria of gastric juice, IF antibodies, agammaglobulinemia
Term
Pernicious anemia Clinical subtypes
Definition
juvenile pernicious anemia- secondary to a variety of conditions, absence of IF factor
Term
Four causes of a folate deficiency
Definition
(1) Inadequate diet
(2) Increased requirement
(3) Malabsorption
(4) Drug inhibition
Term
Laboratory characteristics of Inadequate diet
Definition
vacuolated erythroid precursors, anemia is macrocytic but no megaloblastic
Term
Laboratory characteristics of Increased requirement
Definition
stores are rapidly depleted, hemolytic anemia
Term
Laboratory characteristics of Malabsorption
Definition
intestinal diseases, ileitis, tropical sprune, nontropical sprune
Term
Laboratory characteristics of Drug inhibition
Definition
serum and erythrocyte folate are depressed
Term
Pathophysiology of megaloblastic anemias
Definition
nuclear maturation defect
Term
Peripheral blood of megaloblastic anemias
Definition
macrocytic, normochromic, oval macrocytes, Howell-jolly bodies and hypersegmented neutrophils
Term
Peripheral blood smear for Folate deficiency
Definition
hypersegmented neutrophils
Term
Peripheral blood smears for B12 deficiency
Definition
macrocytes
Term
Vitamin B12 metabolism
Definition
defects in any step of the vitamin B12 metabolism can lead to vitamin B12 deficiency and megaloblastic anemia. Vitamin B12 is released from food via peptic digestion at a low pH in the stomach; it binds to R-protein. In the duodenum, R-factor is degraded and B12 is released and binds to IF, IF and B12 move to ileum where it binds to IF receptors, entire complex is taken into the cell and then B12 is released
Term
Folic acid metabolism
Definition
absorbed in the intestine, folate is reduced into a form that can circulate in the blood, once inside the cell is has to be demethylated in order to stay inside the cell
Term
Vitamin B12 Deficiency
Definition
Deficiency occurs in impaired DNA synthesis and defective fatty acid degradation
Term
Folic acid deficiency
Definition
Deficiency occurs in the decreased synthesis of the circulating form which is a cofactor for DNA synthesis
Term
Macrocytosis associated with a megaloblastic marrow
Definition
macrocytes are not as pronounced; macrocytes are round rather than oval, no hypersegmented neutrophils, normal platelets. Jaundice, glossitis, neuropathy are common
Term
Macrocytosis associated with a normoblastic marrow
Definition
increased membrane lipids, cells usually round
Term
maturation defects that lead to megaloblastosis
Definition
Folate deficiency, B12 deficiency, or chemotherapy, orotic aciduria or CDA
Term
morphologic blood cell abnormalities in meglablastosis
Definition
Macrocytes, normochromic anemia, decreased cell count, Ovalocytes, Howell-jolly bodies, Polychromasia, hypersegmentation of neutrophils
Term
Folate deficiency caused by
Definition
inadequate diet, increased requirement, malabsorption, or drug inhibition
Term
Clincal Symptoms of Folate deficiency
Definition
low income, diseases associated with rapid cell turnover, ileitis, tropical sprune, oral contraceptives, bacteria overgrowth in small intestine
Term
Laboratory results for Folate deficiency
Definition
serum and folate levels decreased
Term
B12 deficiency caused by
Definition
impaired DNA synthesis, defective fatty acid degradation
Term
clincal symptoms of B12 deficiency
Definition
pernicious anemia, gastroectomy, crohn’s disease, tropical sprune, intestinal parasite, strict vegan diets, nitrous oxide inhalation
Term
Causes of pernicious anemia
Definition
absence of IF secondary to gastric atrophy
Term
Clinical variations of pernicious anemia
Definition
juvenile pernicious anemia
Term
Causes of Folic acid deficiency
Definition
inadequate diet, increased requirement, malabsorption, drug inhibition
Term
Clinical forms of folic acid deficiency
Definition
due to different causes
Term
Folate deficiency results in megaloblastic maturation
Definition
due to slowing of DNA synthesis and the S phase if prolonged. Hematopoietic cells show characteristic megaloblastic changes due to folate deficiency. Erythrocytes survive less than 120 days in the peripheral blood
Term
Vitamin B12 deficiency results in megaloblastic maturation
Definition
due to impaired DNA synthesis and defective fatty acid degradation
Term
four laboratory tests used to identify the cause of a macrocytic anemia
Definition
MCV, RBC membrane cholesterol, reticulocytes, morphology
Term
causes of macrocytosis with a normaloblastic marrow
Definition
alcoholism, liver disease, hemolysis, hypothyroidism, aplastic anemia
Term
Macrocytic Anemia MCV
Definition
> 100
Term
Macrocytic retics
Definition
increased
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