Microcytic and Macrocytic Anemias Flashcards
What amount of ingested iron is absorbed?
10%
Iron is stored as ?
Ferritin and homosiderin
Absorbed iron is converted from ?
Ferric (Fe3+) to Ferrous (Fe2+)
What factors affect iron absorption?
GI tract health
Diet (5% daily intake maintains RBCs)
Current iron stores
Erythropoietic need
Identify iron needs in children and adults?
Adults 95% iron is recycled for RBC production
Children 70% iron recycled for RBC production
Why are the iron needs of children higher than adulta?
Children have a higher iron demands because of growth spurts.
What can cause IDA?
Increased iron demans - growth spurts, prenancy, nursing
iron intake - diet / conditions causing iron malabsorbtion
Blood loss - GI bleeding, excessive periods, hemolysis
Unusual symptoms associated with IDA? (3)
Pica - eating weird shit
Chelitis - swollen/ swelling around lips
Koileneychea - spooning of nail beds
What is the iron profile in IDA?
decreased iron
decreased serum ferritin
decreased iron saturation
TBIC increased (more sites available for binding)
Describe the CBC profile in IDA? (6)
What indices is increased?
Decreased RBC count, Hgb, Hct, MCV, MCH, MCHC.
Increased RDW
How many stages are there in IDA? What happens at each stage? At which stage do symptoms start to show?
3 stage 1 - depletion of iron stores stage 2 - ineffective erythroporesis stage 3 - IDA symptoms appear stage 3
What is the most sensitive indicator of iron stores?
Serum Ferritin
Sideroblastic Anemia
Iron overload
Describe the pathophysiology of Hereditary Hematochromatosis and what is it responsible for?
Faulty mechanism cause iron overload.
Iron loading starts at young age.
What is the gene affected in Hereditary Hematochromatosis? How is this disease inherited?
Abnormal HFE gene, responsible for regulating iron storage and absorption.
Autosomal recessive carried on chromosome 6; linked to HLA-A3
inherited homozygously / herterozygously
Homozygotes more prone to iron overload only 10% in hetero
What are some symptoms of Hereditary Hematochromatosis? (6)
Cirrohsis Hyperpigmentation Impotence hair loss Tender swollen joints cardiac arrythmias
Describe the iron profile of patients with Hereditary Hematochromatosis? (5)
Increased serum iron increased ferritin increased tranferrin saturation TIBC normal range Transferrin normal range
How is Hereditary Hematochromatosis treated?
Therapeutic phlebotomy
Desferyl (defroxamine) - iron chelating (binding) agent
What are the Thalassemia syndromes?
Globin chain disorder due to lack of alpha or beta globin chain systhesis.
How many alpha thalassemias are there?
4 - related to the number of genes deleted.
What is the most severe alpha thalassemia?
Bart’s Hydrops Fetalis
Describe the pathology, gene deletions and symptoms in Bart’s?
No alpha chain synthesis only Hgb Bart's formed ( 4 gamma chains) has a very high affinity for oxygen incompatible with life ; severe anemia still birth/ spontaneous abortion
Describe the pathology, gene deletions and symptoms in hemoglobin H disease?
3 gene deletion; 1 functioning alpha gene Hgb H (5 - 40%) formed and little Hgb A Hgb H inclusions: golf ball pitted Symptoms: anemia, splenolmegaly and bone changes
Describe the pathology, gene deletions and symptoms in Alpha thalassemia trait?
2 gene deletion ( 4 functional chains)
Some Hgb Bart’s formed
mild anemia
many microcytic and hypochomic cells
Describe the pathology, gene deletions and symptoms in Silent carrier of alpha THA?
1 gene deletion (3 functional genes)
Hematologically normal
slightly microcytic
peripheral smear will have some elliptocytes and target cells
Cooleys / Mediterranean Anemia
Beta THA Major
Describe the cause of Beta THA major?
little / no beta chain synthesis
What hemoglobin is produced in beta THA major?
Hgb F
How is beta THA major treated? (4)
Transfusion
iron chelation
bone marrow transplant
stem cell transplant
Symptoms of Beta THA Major? (3)
Facial changes, bossing/ protrusion of skull
fail to thrive
jaundice
What Hgb is present in elevated amounts in beta THA minor?
Hgb A2
What is the genetic defect in beta THA minor?
One abnormal beta gene
What are the known clinical manifestation of beta THA intermedia? (3)
develops later in life
minor bone changes
larger spleens
What differentiates Alpha THA from IDA?
MCV much lower than IDA
RDW more severe.
What differentiates Beta THA minor from IDA?
MCV much lower
RBC count is elevated
Except for low MCV, what is a diagnostic clue for Silent Alpha THA?
elliptocytes on smear
What are diagnostic clues for beta THA major?
High NRBCs
target cells, fragments on smear
Describe what a megaloblastic anemia and what a macrocyctic anemia?
meglaoblastic anemia is the result of a B12 or folic acid deficiency and MCV exceeds 110 fL
Explain the role of B12 and Folic acid in DNA synthesis?
DNA sythesis depends on TTP (thymidine triphosphate)
TTP needs methyl group from MTH (methyl tetrahydrofolate) or folic acid.
B12 is the cofactor that transfers the methyl group
If TTP is not made what is it replaced by and what does this lead to?
DTP, leading to nuclear fragmentation, destruction and impaired cell division.
What are the characteristics of megaloblasts compared to normoblasts?
RBC precursors larger
Nuclear structure less condensed (normoblast c: n ratio decreases, nucleus more compact)
Cytoplasm is basophilic and bluer
chromatin open waved (condensed in normoblast)
***Asychronous maturation between nucleus and cytoplasm)
Describe ineffective erythroporesis related to megaloblastic anemias?
Ratio
prcursors
RETIC count
Bilirubin and LDH
M:E ratio 1:1 or 1:3
Megaloblastic precursors hemolyse before maturation complete in bone marrow.
Reticulocytopenia (low RETIC count)
Bilirubin and LDH elevated
The peripheral smear in ineffective erythroporesis related to megaloblastic anemias?
Peripheral smear lacks NRBCs
Describe WBC changes in peripheral smear in MA?
Hypersegmented neutrophils (>5 lobes)
Describe the CBC in MA? (4)
Pancytopenia (low WBC count)
Low RBC count
Low PLT count
MCV initially high
RBC inclusions seen in MA?
BS
HJB (more fragmented and larger)
What happens to the RDW in MA?
RDW increased SCHISTOS TDS TC MACRO MACRO-OVALO
Where is B12 absorbed?
Illeum
What is needed for B12 absorbtion?
Intrinsic Factor (IF)
Where is B12 stored?
Liver; takes years to deplete
What is the MDA for folic acid?
200 micrograms
What is the MDA for B12?
20 micrograms
Where is folic acid absorbed?
Small inntestine
Folic acis is stored long term or short term?
short term; takes months to deplete
Describe B12 transport to bone marrow into red cells?
Ingested and separated by saliva enzymes
In stomach combines with IF
B12-IF complex transported to ileum
B12 absorbed and IF degraded
B12 transported to plasma; complexes with transcobalamin II (TCII)
TCII transports B12 to circulation and transfers to liver, bone marrow and other tissues
What protein transports B12 into circulation and to liver and bone marrow?
Transcobalamin II
How is folic acid transported into tissues?
Absorbed in small intestine
reduced to methyl tetrahydrofolate (MTH) by dihydrofolate reductase - moved to tissues when inside - methyl group released to combine with homocystein
Symptoms of MA?
Glossitis
Neurologic
Mania (personality changes)
Demyelination of peripheral nerves
Dietary B12 deficiency is rare except?
Vegetarians / infants nursed by vegetarian mums who do not supplement diet
Causes of B12 deficiency?
Cobalamin/ intestinal malabsorbtion
food malabsorbtion by helobacter pylori
Blind loop syndrome (basteria take b12)
Fish tapeworm - Diphylobothrium latum competes for B12
Causes of folic acid deficiency?
Pregnancy elderly alcoholics malabsorbtion syndrome - tropical sprue Drug/ chemo drugs affect DNA synth
What is Pernicious Anemia?
Lack Intrinsic Factor needed for B12 absorption
How is B12 deficiency tested for?
Radioimmunoassay
What is the test for Folic acid deficiency?
Chemiluminescence - measures folate stored
How is B12 deficiency differentiated from Folic acid deficiency in the Lab?
Serum methlymalonic acid (MMA) and homocystein.
Both elevated in B12 deficiency, can detect mild B12 deficiency.
How is IF affected in Pernicous anemia?
Can be blocked, neutralized, not secreted:
Gastrectomy
Atrophic gastritis
Antibodies against IF
What do IF antibodies do in PA?
Block B12-IF complex preventing absorption in ileum