mlab 1315- hematology fall 2007 keri brophy-martinez€¦ · ppt file · web view ·...
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MLAB 1415- Hematology
Keri Brophy-Martinez
Chapter 12: Macrocytic Anemias
Macrocytic Anemia Megaloblastic
Abnormal DNA synthesis, usually due to vitamin B12 or folate deficiencies
Results in delayed nuclear development, causing the larger cells
Nonmegaloblastic Mechanism not well defined Increase in membrane lipids
Characterized by large erythrocytes( MCV> 100)
Megaloblastic Anemias “Megaloblast”: large abnormal marrow erythocyte precursor Group of disorders characterized by defective nuclear maturation
caused by impaired DNA synthesis.
Nuclear replication is slowed down resulting in maturation delays, prolonging the premitotic interval Results
Large nucleus Increased cytoplasmic RNA Early hgb synthesis
Megaloblastic Anemias: Clinical Findings
•Anemia is slow to develop•Fatigue• Weakness• Yellow color•Weight loss•Glossitis
Megaloblastic Anemia: Lab Features: Hematology Macrocytic, normochromic anemia
Increased MCH: due to large cell volume Normal MCHC
RBC, HGB, Hct decreased Granulocytes and Thrombocytes are
affected as well. Granulocytes are hypersegmented Megakaryoctyes are abnormal resulting in thrombocytopenia
Megaloblastic Anemia: Lab Features: Peripheral blood
Triad of oval macrocytes, Howell-Jolly bodies and hypersegmented neutrophils
Anisocytosis, Poikilocytosis
RBC’s are fragile, lifespan is shortened and many die in the bone marrow which causes ↑ LDH
Megaloblastic Anemia: Lab Features: Misc
Bone marrow Hypercellular with
megaloblastic erythroid precursors
M:E ratio decreased
Chemistries Vitamin B12 Folate Methylmalonic acid
(MMA) Homocysteine Lactic
dehydrogenase(LDH)
Megaloblastic Anemia: Causes of Vitamin B 12 deficiency Folate deficiency Drugs Myelodysplastic syndromes Acute leukemia
Megaloblastic Anemias: Deficiency of Vitamin B12
Vitamin B12 (cyanocobalamin) deficiency
1. Inadequate dietary intake a. B12 is found in food of animal origin: red
meat, fish, poultry, eggs, dairy products
Megaloblastic Anemias: Deficiency of Vitamin B12
2. Malabsorptiona. Pernicious anemia
Caused by gastric parietal cell atrophy which causes decreased secretion of intrinsic factor (IF). IF is necessary for B12
absorption. Atrophy due to immune destruction of the acid-secreting portion of
the gastric mucosa Onset is usually after age 40, primarily women Affects people of Northern European backgrounds Neurologic problems Schilling test used for diagnosis
Schilling test Establishes the cause of
vitamin B12 deficiency Test performed in two
parts If parts one & two
abnormal: Pernicious anemia
If part one only abnormal: malabsorption
B12 Malabsorption causes (con’t)
c. Gastrectomyd. Blind loop syndrome
bacteria use up the B12
d. Fish tapeworm= Diphyllobothrium latum completes for B12
Other Causes for B12 Deficiency
3. Drugsa. Alcoholb. Nitrous oxidec. Antitubercular drug
Megaloblastic Anemia:Folic Acid (Folate) deficiency
1. Inadequate dietary intakea. Povertyb. Old agec. Alcoholism
Megaloblastic Anemia:Folic Acid (Folate) deficiency2. Malabsorption
a. Ileitis/Crohn’s diseaseb. Tropical spruec. Blind loop syndromed. Nontropical sprue
a. Gluten-sensitive enteropathyb. Childhood celiac disease
Megaloblastic Anemia:Folic Acid (Folate) deficiency
3. Increased requirementa. Pregnancy
a. There is increased demand during pregnancy and should be supplemented prior to and during pregnancy. Deficiency during pregnancy can cause neural tube defects in utero.
b. Infancyc. Hematologic diseases that involve rapid cellular
proliferation such as sickle cell anemia
Megaloblastic Anemia:Folic Acid (Folate) deficiency
4. Drugsa. Methotrexate (chemotherapy drug that is a
folate antagonist)b. Alcoholc. Oral contraceptivesd. Long term anticoagulant drugs
Treatment of megaloblastic anemia
B12 deficiencyVitamin therapyIntramuscular or subcutaneous injections
for pernicious anemia to bypass absorption throught the gut.
Folate deficiencyVitamin therapy
Non-Megaloblastic Anemia
MCV doesn’t go as high as in megaloblastic
Macrocytes are round NOT oval No hypersegmented neutrophils Leukocytes and platelets are normal Jaundice, glossitis and neuropathy are
absent
Non-Megaloblastic Anemia Causes of
Chronic liver disease Alcoholism (alcohol has toxic effect on
RBC’s) Stimulated Erythropoiesis
Anemia associated with liver diseaseCauses of: Blood loss Alcoholism Folate Deficiency Impaired bone marrow
response Hemolysis
Blood Picture: Target cells Acanthocytes Macrocytes Hypochromia Microcytosis
Anemia associated with:
Alcoholism: Ethanol has a toxic effect on precursor cells. Red cells are macrocytic
Stimulated erythropoiesis: Increased EPO, adequate iron Release of stress reticulocytes
References Harmening, D. M. (2009). Clinical Hematology and
Fundamentals of Hemostasis. Philadelphia: F.A Davis.
McKenzie, S. B., & Williams, J. L. (2010). Clinical Laboratory Hematology . Upper Saddle River: Pearson Education, Inc.
http://health.allrefer.com/health/vitamin-b12-vitamin-b12-source.html
http://tiny.cc/hj7iy Turgeon, M. (2005). Clinical Hematology: Theory
and Procedures. Baltimore: Lippincott Williams and Wilkins.