Megaloblastic Anemia megaloast anemia..pdf

megaloblast anemia

1. l-Y
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Doneby:Eshraqsadeq
Supervisor by: Dr.AbdallhAlaleem

3. MegaloblasticAnemia
Macrocytic anemia:
Characterizedbylargesizeerythrocyte(MCV>95)Dueto DNAdisorder
(e.g. Megaloblastic anemia).
Divided into:
-Non-Megaloblastic(non-megaloid,Macrocytosis).
-Megaloblasticanemia(megaloid)enlargederythroid precursor.
Non-Megaloblastic (Non-megaloid, Macrocytosis)
Enlarged RBCs in the peripheral blood with normal erythrocyte production from
the bone marrow.

4. MegaloblasticAnemia
Causes:
Macrocytic anemia (Macrocytosis)
MacrocytosiswithNormoblasts
(erythroidprecursureisnormal)
Alcohol1 (mostcommon)
Liver2 disease(especially alcoholic)
Reticulocytosis 3 (increase in haemolysis
or haemorrhage) RBCs in the stage
before maturation, giveswrong
reading.
Hypothyroidism.4
Myelodysplasia MDS 5 including
acquired Sideroblasticanaemia.
Pregnancy.6
Newborn.7
Normal1 neonates
(Physiological)
Chronic2 alcoholism*
My3elodysplastic syndromes*
Chronic4 liverdisease*
Hypothyroidism5
Normal6 pregnancy
Therapy 7 with anticonvulsant
drugs*
.Myeloma and 1
macroglobulinaemia.
.Leucoerythroblastic anaemia.2
.Myeloproliferative disease.3
.Aplastic anaemia or red cell aplasia.4
.Chronic respiratory failure.5
.Haemolyticanaemia.1
.Chronic2 lungdisease (with
hypoxia).
.Hypoplastic and 3 aplastic
anaemia.
.Myeloma.4
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5. MegaloblasticAnemia
REMEMBER:
Non-megaloblasticanemia (Macrocytosis): abnormalityisintheperipheral
blood,notinthe bonemarrow.
MacrocytosiswithNormoblastscanbenormalin neonates.
Megaloblasticanemia
It’sagroupofanemiasthatresultsfromtheabnormal synthesisofDNAduring
erythropoiesisinthebonemarrow. (AsynchronousDNAsynthesis:maturationofthe
RBCs nucleusbeing delayedrelativelytothatofthe cytoplasm).
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6. Most importantfeatures ofmegaloblasticanemia are:
-Macrocytes(largecells).
-Hypersegmentedneutrophils (classical in vitamin B12
deficiency): mainly found in megaloblastic anemia but could
appearinnon-megaloblastic incasesof:
1-Renalfailure
2-Congenital(familial)abnormality
NOTE:
-AbnormalDNAsynthesiswillinhibitthedivisionofthecells,whichwill
makethecellbigger.
-Perniciousanemiaisassociatedwithdeficiencyofvit B12orfolicacid.

7. MegaloblasticAnemia
Causesofmegaloblasticanemia:
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1-Cobalamin (vitamin B12) deficiency or abnormalities of cobalamin metabolism most
common.
2-Folate deficiency or abnormalities of folate metabolism 2nd most common.
3-Therapywith antifolatedrugs (e.g. methotrexate)
4-Independent of either cobalamin or folate deficiency and refractory to:
a) Some cases of acute myeloid leukemia, myelodysplasia. (Poor absorption of folate
and cobalamin).
b) Oroticaciduria(responds to uridine)
c) Therapy with drugs interfering with synthesis of DNA (e.g. cytosine arabinoside,
hydroxyurea, 6-mercaptopurine, azidothymidine(AZT)
d) Thiamine responsived

8. MegaloblasticAnemia
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5-Suggested but poorly documented causes of megaloblastic anaemianot due to
cobalamin or folate deficiency or metabolic abnormality:
a) Vitamin E deficiency.
b) Lesch-Nyhansyndrome (responds to adenine).
6-Abnormalities of nucleic acid synthesis
a-Drug therapy:
Antipurines(mercaptopurine, azathioprine)
Antipyrimidines(fluorouracil, zydovudine(AZT))
Others (hydrozyurea)
b-Oroticaciduria(abnormality in DNA synthesis).
7-Uncertain aetiology.
8-Myelodysplastic syndromes, * erythroleukaemia.
9-Some congenital dyserythropoieticanaemias.
* Some patients show normoblasticerythropoiesis (these causes are not
characteristic).
Other causes : (Not Important)
REMEMBER:
1.Megaloblastic anemia due to inhibition of DNA synthesis and affect RBCs in the
bone marrow.
2.Most common causes of megaloblastic anemia B12 deficiencythen folic acid
deficiency.

9. MegaloblasticAnemia
VitB12&folatenutritionandabsorption:
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VitaminB12 Folate
Dietarysource
Only food of animal
origin, red meat,
especiallyliver
Most foods, especially
liver, green vegetableandyeast;
destroyedbycooking.
Averagedaily intake
7-30µg 200-250µg
Minimumdaily
requirement
1-3µg 100-200µg
Time to develop
deficiencyinthe absence
of intake or absorption*
Anemiain2-10 years Macrocytosisin5 months.
Requirements for
absorption
Intrinsic factor secreted
by gastricparietal cells
Conversion of polyglutamates
to monoglutamatesby
intestinal folate conjugase
Site of absorptionTerminalileum Duodenumand jejunum

11. VitaminB12

12. Biochemical function
Vitamin B12 is a coenzyme for two biochemical reactions:
first, as methyl B12 it is a cofactor for methionine synthase,theenzyme
responsible for methylation of homocysteine to methionine using methyl
tetrahydrofolate (methyl THF) as methyl donor
second, as deoxyadenosylB12 (ado B12) it assists in conversion of
methylmalonylcoenzyme A (CoA) to succinylCoA

13. MegaloblasticAnemia
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:
VitaminB12

14. 1-Inadequate intake. 2-Veganism, lactovegetarianism(some cases)
3-Inadequate secretion of intrinsic factor 4-Pernicious anemia
5-Total or partial gastrectomy. 6-Congenital intrinsic factor deficiency (rare).
7-Inadequate release of B12 from food.
8-Partial gastrectomy (common, bypass surgery), vagotomy, gastritis, acid-
suppressing drugs, alcohol abuse.
9-Diversion of dietary B12.
10-Abnormal intestinal bacterial flora multiplejejunaldiverticula, small intestinal
strictures, stagnant intestinal loops.
11-Diphyllobothrium latum(fish tapeworm).
12-Malabsorption (one of the main causes).
13-Crohn’s disease, ilealresection, chronic tropical sprue, congenital selective
B12malabsorption with proteinuria (Imerslund-Grasbecksyndrome).
Causes of vitamin B12 deficiency
NOTE:
Ingestion of food containing vitamin B12Parietal cell in stomach secrete intrinsic
factor bend to B12 in terminal ileum get absorbed by TC2(transcobalamin2) in
the terminal ileum. Anything will interfere with this process will cause vitamin B12
deficiency.

15. MegaloblasticAnemia
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vitaminB12absorptionpathway
Dietary absorption of vitamin B12 is a complex process thatbeginswithhaptocorrin
(alsoknownas transcobalamin I or R-binder) production by the salivary glands.
When food is digested in the stomach by gastric acid and pepsin,freevitaminB12is
releasedandbindsto haptocorrin.
gastricparietalcells secrete intrinsic factor, which cannot interactwiththe vitaminB12-
haptocorrincomplex.
Not until food moves into the duodenum, where trypsin andotherpancreaticenzymes
cleavehaptocorrin,is vitaminB12freetobindtointrinsicfactor.

16. MegaloblasticAnemia
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ThevitaminB12-transcobalamincomplex thenbindsto the transcobalaminreceptors
on hematopoietic stem cells (andothercelltypes),allowinguptakeofthecomplex,
with-subsequentlysosomaldegradation--of transcobalamin.FreevitaminB12is
thenavailablefor cellular metabolism.
TheresultantvitaminB12-intrinsicfactorcomplexbindsto thecubamreceptor
onthemucosalsurfaceof enterocytesintheileum.Fromthere,vitaminB12is
transported into the circulation by multidrug resistance protein1,whereitis
readilyboundbyitstransportprotein transcobalaminII.

18. MegaloblasticAnemia
Folate:
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DietaryFolatemustbeconvertedtomythelTHF (tetrahydrofolate) to get absorbed in
the small intestine. ThenwiththehelpofB12andhomocysteine,mythelTHFwillbe
convertedtoTHF.
happenabsentthereactionwon’t
Ifanyoneofthethree:mythelTHF,homocysteineorvitB12i
-Folateabsorbtion
mainlyinjejunuminthe formofa reducedmonoglutamate(methylTHF).
-Methyl-THFmonoglutamateistheformoffolate itis foundinserum.
-Folic acidconjugatesinhydrolysedbyconjugases to
pteroylmonoglutamicacid.
conjugases are enzymes present in vegetables and mammaliantissue,GITmucosa
&pancreas
Pteroylmonoglutamicacid(Methyl-THF)is completely
absorbedinsmallintestinejejunum.
Transport,storageandfate:
Folic acidtransportincirculation as N5 Methyl-THF mostlyis looselyboundtoalbumin
fromwhere itiseasily taken upbycells.
N5 Methyl THF inside cells converted to THF (polyglutamateforms) by cobalamine
enzyme methionine synthetase.

19. MegaloblasticAnemia
-Vit-CprotectsTHF fromdestruction.
-Totalfolateinbody:5-10 mg(1/3storeinliveras N5-methylTHF),N5-
methyl-THFishighlyboundtoalbumin.
Functions offolicacid:
Transferofmethyl orformylgroupstoothercompounds. Eg.: duringthe
productionofthymidylateforthesynthesis ofDNA (methylationof
deoxyuridylate)
THFAmediatesnumberofoneCarbontransferreactions.
THFAplayroleinconversionofhomocysteineto methionine.
THFAplayroleinGenerationofthymidylate.
THFAplayroleinConversionofserinetoglycine.
THFAplayroleinPurinesynthesis.
THFAplayroleinHistidinemetabolism.-
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21. Causes of folate deficiency:
1. Inadequate dietary intake.
2. Malabsorption: (Coeliac disease, jejunalresection, tropical sprue)
3. Increased requirement: (Pregnancy, premature infants, chronic haemolyticanemia,
myelofibrosis, various malignant diseases)
4. Increased loss: (Long-term dialysis, congestive heart failure, acute liver disease)
5. Complex mechanism: (Anticonvulsant therapy, * ethanol abuse*)
•Only some cases with macrocytosisare folate deficient.
6-Drug
(Oralcontraseptivedrugs,Someanticonvulsant drugs,Triamterene
,Cholestyramine).

22. MegaloblasticAnemia
Clinical FeaturesofMegaloblasticanemia
1-Weakness,anorexia,weightloss,diarrheaor constipation, tiredness, shortness of
breath, angina of effort,heartfailure.(duetolowHemoglobin).
2-Mildjaundice(hemolyticanemia),glossitis(with enlargement and redness of the
tong) (beefy tongue), stomatitis,angularcheilosis.(Fissuresaroundthelips).
3-Purpura,melaninpigmentations.
4-Infections.
.15-Neuropathydue tovitB12andfolatedeficiency: It’s mostly due to vitamin B12
deficiency. Progressiveneuropathyaffecting:
-Theperipheralsensory nerves.
-Posteriorandlateralcolumnsofthespinalcord (subacute combined
degenerationofthe cord).
-Opticatrophy.
Psychiatricsymptoms.(e.ghallucination).
-The neuropathy is likely due to accumulation of S-adenosylhomocysteineand
reducedlevelofS-adenosyl methionine in nervous tissue resulting in defective
methylationofmyelinandother substrates.
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24. MegaloblasticAnemia
6.Neuraltubedefect(NTD):
-(Anencephaly, spina bifida or encephalocoele) in the fetus due to folateor Vitamin
B12deficiency in the mother. This result in build-up of homocysteine and S-
adenosylhomocysteineinthefetus,whichimpair methylationofvariousproteins
and lipids.
-Genetic a mutation in the parents in 5,10 methylene tetrahydrofolatereductase
(absenceofthis enzyme)lowserumredcellandfolateandhigh serum
homocysteine and fetus with NTD. -Cleft palate andhairlip.
*NTDhappensduetodeficiencymorethanGenetic
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7-highriskofthrombosis.
REMEMBER:
Vitamin B12 deficiency. Neuropathy and hypersegmentedneutrophils are
classical to

25. MegaloblasticAnemia
Hematologicalfindings inMegaloblasticAnemia:
PeripheralBlood:
Macrocytic anaemia, oval macrocytes, anisocytosis,
poikilocytosishigh MCV.
Dimorphic anemia when it is associated with iron
deficiency or with thalassaemiatrait.
.
-Hypersegmentedneutrophils.
-Leucopeniaandthrombocytopenia.
-Bazophilicstippling
-Howell-Jollybodies
-Cabotring
-Nucleatedredcells
RBCIndexes:
MCV:Increased
MCH:Increased
RDW:Increased
WBC:
Neutrophyls:hypersegmentation(anearlysignof megaloblastichematopoiesis).
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Cabotring

27. Pancytopenia may be seen in advanced cases. In severe anemia with a
hematocrit of less than 20%, promegaloblastsand nucleated erythrocytes may
be seen, caused by extramedullaryhematopoiesis in the spleen and very early
marrow release. A dimorphic population of red cells may be present with
concurrent iron deficiency. The red cell distribution width is high.

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Bone Marrow:
-Hypercellularmarrow with M:E ratio in normal or reduced.
-Accumulation of primitive cells due to selective death of more mature cells.
-Megaloblast(large erythroblast which has a nucleus of open, fine, lacy chromatin).
-Dissociation between the nuclear and cytoplasmic
development in the erythroblasts.
-Mitosis and dying cells are more frequent than normal.
-Giant and abnormally shaped, metamyelocytes, polypoidmegakaryocytes. (most
important finding).
-Increased stainable iron in the macrophage and in theerythroblasts.

30. MegaloblasticAnemia
Biochemicalfindings
↑ urobillinogenand faecalstercobillinogen.
↑ LDH↑ serumiron↑bloodcarbonmonoxide.
↑Serumlysozyme.
↓Reducedhaptoglobins.
↑Bilirubin(indirect)
↑assayforNitric oxide.
ConfirmationandSpecialLabtests
VitB12deficiency:
Serum VitB12 ↓
↑Methylmalonicacid excretion increased
Formiminoglutamate(FIGlu)excration50% cases.
-Radioactive VitB12 absorbtipontest
-Deoxyuridinesupressiontest
-Hyperhomocysteinemia-
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31. Folatedeficiency:
Serum folate↓
RBC folate↓
Formiminoglutamate(FIGlu) excretion ↑
-Deoxyuridinesupressiontest .
-Hyperhomocysteinemia.
Otherlaboratoryabnormalities
Chromosomal abnormalities
-Ineffective haemopoiesis. (Intramedullary cell death by
apoptosis) associated with increased serum indirect bilirubin.

32. MegaloblasticAnemia
Treatment:
1. Even if the diagnosis is confirmed we must test for vit B12andfolicacidlevels.
Largeamountofhydroxocabalaminneuraldefectin pregnantladies.
-
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33. Asuccessful response to treatment with cobalamin (vitamin
B12) or folate begins within 8 to 12 hours in the bone marrow, with
resolution of megaloblastic hematopoiesis. The reticulocyte count
begins to increase 2 to 3 days after treatment and peaks in 5 to 8
days; higher and later peaks occur in more severe anemia. The
hematocrit begins to increase in approximately 1 week and will
normalize within 4 to 8 weeks. The MCV typically increases for the fi
rst3 to 4 days, presumably because of reticulocytosis, and then
begins to decrease. The normal reference range is expected to be
reached in 25 to 78 days. Resolution
of neurological abnormalities is dependent on the duration of loss.
Most neurological symptoms will show maximal improvement
within 6 months of initiation of therapy. Serum iron levels will begin
to fall within 24 hours of successful treatment, but the patient must
be observed over the next 2 to 3 weeks.

34. MegaloblasticAnemia
Perniciousanemiaand autoimmunegastritis
-Chronic atrophic autoimmune gastritis is an autoimmune process directed
specifically at either gastric parietal cells or intrinsic factor, or both.10–12
Parietal cell damage leads to reduced production of gastric acid and intrinsic
factor, accompanied by a compensatory increase in serum gastrin levels.
-Decreased intrinsic factor leads to significantly reduced absorption of dietary
vitamin B12, resulting in pernicious anemia.
-Congenital pernicious anemia:characterized by the total absenceofIFandnormal
secretionofothergastricjuices.
Pathophysiology of PA : The main cause is atrophic
gastritis characterized by atrophy of gastric mucosa with decrease of gastric
secretions & IF.
--The cause of gastric atrophy however is not clearly known.
--But it is postulated that genetic, immunologic, and
-environmental factors all play a role.
---IF is essential for absorption of vit-B12.
--In absence of IF, only a small amount of vit-B12 is
-absorbed
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35. MegaloblasticAnemia
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Clinical Features: The common features are anemia
(angina effort), paraesthesia, Glossitis, recurrent
diarrhoea, anorexia, weight loss, abdominal pain,
mental disturbance, and visual disturbance.
Lab. Diagnosis:
Hbdecreased (7-9 g/l up to 3g/dl, occasionally is
normal).
MCV is increased
MCH is variable and
MCHC is normal or slight increase (33-38 pg)
Blood Smear:
• Macrocytic oval cells,
• nucleated RBCs,
• containing Howell-Jolly bodies,
-A moderate leukopenia, hypersegmentedneutrophils.
-A few myelocytesmay appear in the pb.
-A moderate thromocytopeniais usual with platelet
count 100000-150000/mL
Pancytopenia and reticulocytopeniaare prominent
features of the megaloblastic processes

36. MegaloblasticAnemia
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Increase numbers of early erythroblasts and increase mytosis
Schilling test(obsolete): consist of tow parts
Although Schilling test is not a recommended procedure, an explanation
provides some insights into megaloblastic process and pernicious anemia.
In Part1:theprocedure:
give the patient oral dose of vit-B12 and then, within 2 hours,
give a flushing dose of vit-B12 via intramuscular injection.
The flushing dose saturates all of liver vit-B12 binding sites.
The urine is collected in a 24-hour period, and the amount of vit-B12 is measured.
If IF was present and vit-B12 was absorbed, 5% to 30% of the initial radio-labeled vit-B12
would be excreted.
If less than this amount is excreted, some type of malabsorption has occurred..
Bone marrow:
low M:E ratio and Hypercellularand with erythroblast hyperplasia are seen
large and show open, fine, lacy primitive chromatin pattern but normal
cytoplasmic haemoglobinization,
-Giant erythroblasts called megaloblasts

37. MegaloblasticAnemia
Inpart2:
Oral IF is added to vit-B12 radiolabeled dose, and the test proceeds as in part
1, including the flushing dose of vit-B12.
If excretion of vit-B12 is in proper amount, IF is determined as the deficiency.
If the excretion of vit-B12 is less than expected, the patient is diagnosed with
a malabsorption syndrome.
Treatment
-life long
-cobalamine replacement
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38. MegaloblasticAnemia
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39. When macrocytesappear in the peripheral smear, it is important to observe
them carefully for shape, color, or hypochromiabecause these
morphologic clues can aid in determining if the macrocytosisis
megaloblastic or nonmegaloblastic.
Megaloblastic macrocytesare large and oval, with a thicker exterior
membrane and lacking hypochromia.
Macrocytesin the peripheral smear that lack any of these characteristics are
usually not of megaloblastic origins.
Macrocytosiswith hypochromic may seen in conditions such as:
hemolytic anemia,
hypothyroidism,
chronic liver disease, alcoholism,
chemotherapy treatment, or a myelodysplastic disorder.
Additionally, a macrocytic blood picture is noted in newborns because
their bone marrow is immature and rapidly delivering nucleated cells
and reticulocytes.
*Macrocytic Anemias other than Megaloblastic:

41. MegaloblasticAnemia
-MegaloblasticAnemia:Overview-eMedicineHematology".Retrieved2009-02-07.
-Bain,BarbaraJ.;Bates,Imelda; Laffan,MikeA.(2016).DacieandLewisPractical
-HaematologyE-Book.ElsevierHealthSciences.ISBN9780702069253
.
-Hoffbrand’sEssentialHaematology
Clinical Laboratory Education Consultant Mary L. Turgeon & Associates 2012.
RODAK’S HEMATOLOGY: CLINICAL PRINCIPLES 2016-
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References