ANEMIAS OF ABNORMAL NUCLEAR DEVELOPMENT: Megaloblastic Anemia

Etiology

Vitamin B12 deficiency/Pernicious anemia

Folate deficienc

Combined deficiencies

Etiology: Pernicious Anemia

Gastric atrophy

Results in decreased secretion of intrinsic factor (IF) by parietal cells

Destruction of vitamin B12 in GI tract

Other causes

Etiology: Folate Deficiency

Dietary deficiencyAlcoholic cirrhosisPregnancyInfant malnutritionFolate antagonists

Pathophysiology

B12 and folate deficiencies result in

defective DNA synthesis

This results in an abnormal cell maturation processMost likely megaloblastic cells die in the bone marrow

Major Clinical Characteristics

B12 deficiency: Neurologic symptoms,

glossitis (beefy red tongue); gastrointestinal symptoms

Folate deficiency: Similar to features above, but without neurological

problems

Megaloblastic Anemia:Laboratory Testing

HemogramMorphologyBone marrow examination (rare)Serum B12

Serum folateOther tests

Hemogram Pattern in Megaloblastic Anemia

WBC N/Hgb MCVPLT N/

Peripheral Blood Morphology

AnisocytosisMacro-ovalocytesPossible megaloblastsGiant and hyperseg-

mented neutrophils (PA polys)Possible granule deficient platelets

DARAH TEPI

Macrocyte vs. Macrocyte

Macroovalocyte

RPI<2

PolychromatophilicMacrocyte

RPI>3

Bone Marrow Findings

HypercellularPredominantly megaloblastic erythropoiesisGiant granulocyte precursorsNuclear-cytoplasmic asynchronyPossible decreased megakaryocytes

and nuclear changes

BMP ANEMIA MEGALOBLASTIK

Megaloblastic vs. Megaloblastoid

Megaloblastic Caused by B12 or

folate deficiency

All blood cell lines affected

Megaloblastoid Not caused by B12 or

folate deficiency; seen in myeloproliferative and myelodysplastic disorders

Selected cell lines affected; other nuclear anomalies may be present

Serum B12 and Folate Assays

Principle: Competitive protein binding

radioimmunoassay

Serum B12 and Folate Assays

B12

57Co

IF

F

L125I

IF

L

F

125IF

125I

B12

B12

57Co

57Co

B12 Pt’s Vitamin B12

F Pt’s Folate

57Co 57Co-labeled cobalamin

125I 125I-labeled folic acid

IF Intrinsic factor L -lactoglobulin

Serum B12 and Folate Assays

Washing to remove unbound radioactive labels

-scintillation countingResidual radioactivity is inversely

proportional to the amount of patient’s B12 and folate

Result determined by comparison to standard curve

Serum B12 and Folate Assays

Specimen requirements Serum preferred EDTA plasma acceptable Fasting specimen for folate Avoid hemolysis for folate assay

Serum B12 and Folate Assays

Specimen storage Protect from light (folate) 2-8°C for 3 hours -20°C longer periods

Specimen preparation: boiled or exposed to an alkaline agent

Serum B12 and Folate Assays

Reference ranges Serum B12: 100-700 pg/mL Serum Folate: 3-16 ng/mL

Lower limit for B12 deficiency not well defined

In untreated patients with folate deficiency levels are usually <1.0 ng/mL

Other tests may be needed in borderline cases

Other Tests

Schilling testUrine formiminoglutamic acid (FIGlu):

Increased in B12 and folate deficiencyUrine/serum methylmalonic acid

(MMA) Specific for B12 deficiency

Elevated in B12 deficiency

TreatmentIntramuscular injections of vitamin B12 every

1-3 monthsEffects

Increased retic count in 5-7 days HCT in reference range in 1-2 months Other RBC parameters return to normal Hypersegmented neutrophils disappear in 2

weeks

Platelet count normal within 7 days