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Faculty of Applied Medical SciencesDepartment Of Medical Lab. TechnologyDepartment Of Medical Lab. Technology2nd Year – Level 4 – AY 1433-1434

Mr. Waggas Ela’as, M.Sc, MLTMr. Waggas Ela’as, M.Sc, MLT

MEGALOBLASTIC ANEMIAS

Define Macrocytic anemias and relate them to

megaloblastic anemias. Discuss the normal metabolism of B12 & folic acid Discuss the role of B12 & folic acid in nuclei maturation Describe the clinical presentation of megaloblastic

anemias. List and discuss lab findings and diagnosis of megaloblastic

anemias. Compare megaloblastic anemias caused by B12 deficiency

with folic acid deficiency. Discuss and describe Pernicious anemias and Schilling test.

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Objectives

These are the anemias in which the RBC have an

MCV of greater than 96 fl. There are 2 groups of macrocytosis1. Megaloblastic anemia2. Non megaloblastic macrocytosis, which includes : Alcohol, Liver disorders, cyotoxic drugs, a plastic

anemia, pregnancy, smoking, reticulocytosis, neonatal, myeloma, Hypothyroidism , Myelodysplastic syndrome , Scurvy (Vit-C dif)

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MACROCYTIC ANEMIAS

Group of disorders in which erythroblasts in

the bone marrow, show delayeddelayed nuclear nuclear maturationmaturation relative to that of cytoplasm, due to defective DNA synthesis.

When DNA synthesis is impaired, the cell cycle cannot progress to mitosis. This leads to continuing cell growth without division, which presents as macrocytosis.

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MEGALOBLASTIC ANEMIAS

The most common causes are : 1. B12 deficiency

2. Folic acid deficiency. Other causes include : 1. Abnormalities of B12 or folate metabolism (e.g :

transcobalamin deficiency, nitrous oxide, anti folate drugs)

2. Defects in DNA synthesis ( congenital or acquired enzyme deficiency)

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Causes of Megaloblastic anemia

Synthesized ONLY by microorganisms, and animals

acquire it by production from intestinal bacteria, by eating other animal foods or by eating bacterially contaminated foods.

Found in liver, meat, fish, dairy products. Does not found in fruit, cereals or vegetables.

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B12 (cobalamin)

In stomach, Bl2 is combined with the intrinsic factor (IF)

which is synthesized by the gastric parietal cells. The IF-B12 complex can then bind to a specific surface

receptor in distal ileum where it is absorbed and IF destroyed.

Vitamin Bl2 is absorbed into portal blood where it becomes attached in the plasma to transcobalamin (TC) which delivers Bl2 to bone marrow and other tissues.

(Note the similarity between Transcobalamin & Transferrin)

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Absorption of B12

Megalobastic anemia due to B12 deficiency, occurs

in TC deficiency, although serum B12 is normal. Why?

Because B12 is bound to Haptocorrin (an other plasma protien synthesized by granulocytes & macrophages).

Haptocorrin Is unable to deliver B12 to bone marrow and other body cells.

Function of B12 : needed in the conversion of Methyl THF to THF, a step in the DNA synthesis.

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1. Nutritional - low intake : vegans2. Malabsorption Gastric causes (Pernicious anemia, congenital lack

of IF, total or partial gastrectomy). Intestinal causes (tropical sprue) Fish tapeworm. (Diphyllobothrium latum absorbing 80% or more

of the host’s B12 intake)

(Tropical sprue is a chronic diarrheal disease, possibly of infectious origin, that involves the small intestine and is characterized by malabsorption of nutrients, especially folic acid and vitamin B12) 9

Causes of Vit.B12 deficiency

Is a parent for a large group of compounds, the folates. Humans are unable to synthesize folate structures. Leafy vegetables are a principal source Folate is needed in many biochemical reactions in DNA

synthesis. Folate as 5,10 methylene tetrahydrofolate (THF) polyglutamate, is required in the synthesis of thymidine monophosphate to form eventually the DNA and to repair it.

It has no specific plasma protien facilitate transport.

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Folic acid

1. Nutritional (old age, poverty, special diets)2. Malabsorption :Tropical sprue, partial gastrectomy, jejunal resection)3. Increased requirements:

- pregnancy and lactation- infancy- malignancy- hemodialysis

4. Excess urinary loss(active liver disease, congestive heart failure) 5. Drugs (anticonvulsants)5. Mixed (liver disease, alcoholism)

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Causes of Folic acid deficiency

Vitamin B12

Folic acid

Main foods Animal produce only Liver, greens & yeast

Minimal Daily requirement

1 - 2 µg 100 -150 µg

Body stores 2 – 3 mg (sufficient for 2-4 years)

10-12 mg (sufficient for 4 months)

Cooking Little effect Easily destroyed

Places of absorption ileum duodenum & jejunum

Absorption Intrinsic factor Conversion to MTH

Normal values in serum 160 – 925 ng/l 3.0 – 15.0 µg/l

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VITAMIN B12 AND FOLIC ACID- nutritional aspect

1. Symptoms of anemia 2. Symptoms associated with vit. B12 or Folic acid deficiency ◙ Neurologic symptoms (exclusivly in severe Vitamin B12 deficiency)

: numbness خدر and tingling تنميل in the hands and feet.

◙ Gastrointestinal (vit.B12 and folic acid deficiency)

- loss of appetite

- glossitis (beefy red, painful tongue)

- angular stomatitis 3. Jaundice due to ineffective erythropoesis.

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MEGALOBLASTIC ANEMIAS clinical features

1. Diagnosis of megaloblastic anemia (by doing blood

count, blood films, Biochemical tests & bone marrow examination).

2. Establishing a type of deficiency (vit. B12 and/or folic acid) . By estimating serum B12, serum folate, Red cell folate.

3. Establishing a cause of deficiency (by doing absorption tests : e. g : Schilling test)

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Laboratory Diagnosis

A. Blood cell count: macrocytic anemia ( Low Hb with MCV>100fl ) Low Platelets & Leucocytes count. low reticulocyte count B. Blood film : Macrocytosis (oval macrocytes) , anisocytosis. hypersegmentation of Neutrophils. (more than 5 lobes

nucleus)

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Diagnosis(1)

Blood film

Hyper segmented neutrophil Normal Neutrophils

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Blood film (cont.)

Macrocytic red cells Normocytic red cells

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Compare the red cell size to the nucleus of small Lymphocytes

C. Laboratory findings Hyperbilirubinemia Elevation of lactate dehrogenase (LDH)

D. Bone marrow smear Hypercellular Increased erythroid /myeloid ratio Erythroid cell changes (megaloblasts: an abnormally large

cell with nuclear- cytoplasmic asynchrony : open, fine, primitive chromatin but normal Hemoglobinization)

Myeloid cell changes : Giant metamyelocytes. Megakaryocytes are decreased and show abnormal

morphology 21

Diagnosis(1)

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Bone marrow

In B12 deficiency In Folic acid deficiency

Serum B12 : reduced Serum B12 : Normal

Serum folate : increased

Serum folate : reduced

Red cell folate : reduced

Red cell folate : reduced

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Without B12 deficiency, red cell folate is more accurate than serum folate for tissue folate status . Why?Because red cells acquire folate when they are produced, and the cellular concentration of folate does not change during the red cell lifespan. A single folate-rich meal can correct the serum folate in a deficient patient, while a persistently low red cell folate reflects chronically depleted stores.

Diagnosis (2): Establishing the type of deficiency

The Schilling testSchilling test is used to determine whether the body absorbs vitamin B12 normally.(to find the cause of low vitamin B12 levels).

One µg of radioactiveradioactive B12 is taken orally. One hour later, a 1000 µg injection "flushing" dose of non-

radioactive B12 is given to saturate B12 binders (Transcobalamines)

Radioactive B12 is excreted in the urine; and assayed for its content of radioactivity.

A second stage may be needed, in which the first step is a combination of B12 and IF.

Diagnosis (Diagnosis (33):): Establishing a cause of deficiency Establishing a cause of deficiency (Schilling test)(Schilling test)

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Pernicious anemia is an autoimmune disease that affects the

gastric mucosa and results in gastric atrophy. Antibodies are produced against cells of the stomach or against

IF. This leads to the destruction of parietal cells and failure to

produce intrinsic factor, resulting in vitamin B12 malabsorption . If pernicious anemia is left untreated, it causes vitamin B12

deficiency, leading to megaloblastic anemia and neurological disorders, even in the presence of adequate dietary intake of vitamin B12.

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pernicious anemia

1. What is the difference between Megaloblastic and

pernicious anemia?

2. Which ONE of the following is NOT TRUE about megaloblastic anaemia?

I. It is always caused by B12 or folate deficiency

II. Bone marrow appearances are identical in B12 or folate deficiency

III. It is caused by defective DNA synthesisIV. It may be caused by nitrous oxideV. It is associated with jaundice

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Homework-4

A 32 year old male is admitted to the emergency department

suffering from multiple gunshot wounds to the abdomen. Surgery results in removal of the all of the jejunum. Several months later, the patient complains of being tired. A CBC indicates an increased MCV of 125, decreased Hb and Hct. Which of the following is consistent with these data? Why?

a)iron deficiency anemiab)anemia of chronic diseasec)Vit B12deficiencyd)Folate deficiencye)Sideroblastic anemia

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3 .Case