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Pathology Term 3 > Week 4 - RBC HAEMATOLOGY > Flashcards

Week 4 - RBC HAEMATOLOGY Flashcards

Intro. to Anemia, Deficiency Anemias, Hemolytic Anemias (Acquired/Congenital), Anemia Summary

1
Q

What is the normal size of a reticulocyte?

A

MCV > 100fL (fentolitre)

-normal RBC = 80-100fL

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2
Q

What is the definition of anemia and what are the 2 broad types?

A

Decreased red cell mass affecting tissue oxygenation

  1. Decreased production (DEFICIENCY anemia)
  2. Increased loss/destruction (HEMOLYTIC anemia)
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3
Q

How is anemia diagnosed?

A
  • diagnosed using hematocrit (HCT) or hemoglobin (Hb) levels

- will be decreased HCT and Hb

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4
Q

What type of anemias come under the decreased production category?

A 
Nutrient deficiency
-IDA
-MBA
Hemopoietic cell defect
-ACD
-AA
-dysplastic anemia; myelodysplastic syndromes
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5
Q

What type of anemias come under the increased loss/destruction category?

A

Blood loss anemia –> acute/chronic (peptic ulcer) bleed
Hemolytic anemia –> acquired/congenital

Acquired:

  • external injury –> drugs, mechanical, parasites, infection
  • immune –> AIHA (warm/cold)

Congenital:–> internal RBC defect

  • defective membrane –> hereditary spherocytosis
  • defective hemoglobin –> sickle cell/thalassemia
  • defective enzyme –> G6PD deficiency
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6
Q

What is the microscopic difference between reticulocyte and erythrocyte?

A
  • reticulocyte has the reticular network of cytoplasmic RNA still –> bluish appearance
  • when Hb fills up more, cytoplasmic RNA is extruded –> erythrocyte
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7
Q

Outline RBC development

A

Hemocytoblast –> proerythroblast –> early erythroblast (ribosome synthesis) –> late erythroblast (Hb accumulation) –> normoblast –> reticulocyte (ejection of nucleus) –> erythrocyte

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8
Q

What are the 2 important constituents for RBC production?

A
  1. Hb
    - requires iron
  2. DNA
    - Thymidine (T) requires B12/folate
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9
Q

True or False?

avg. normal RBC is bigger than average width of a capillary

A

True

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10
Q

What are the 2 important nutrients for DNA metabolism and what is the consequence of deficiency of these?

A

B12 + Folate

  • necessary for DNA metabolism (specifically thymidine)
  • deficiency = decreased DNA maturation = decreased ability for RBCs to fully divide –> MBA
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11
Q

What is the commonest cause of IDA and what are the others?

A
  • BLEEDING = commonest
  • nutrition
  • increased needs (physiological growth, childhood, pregnancy
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12
Q

What is the major source of iron for use in the body?

A

recycling of RBCs

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13
Q

Why is bleeding such a big issue for IDA?

A
  • loss of iron in blood –> IDA
  • iron has a very poor absorptive/excretory capacity
  • MAJORITY of iron is obtained from recycling of RBCs
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14
Q

What is the pathogenesis of IDA and what is the morphology?

A

Patho:
-decr. iron –> decr. Hb –> decr. MCV (normal DNA synthesis = increased cell division)

Morphology:

  • microcytic, hypochromic cells
  • anisopoikilocytosis
  • pencil cells
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15
Q

What are the clinical features of IDA?

A
  • *iron is necessary for fast dividing cells (EPITHELIUM)
  • -> damage in epithelial tissues
  • glossitis, chelitis, stomatitis –> also seen in MBA
  • koilonychia –> specific for IDA
  • dysphagia –> due to epithelial damage in oesophagus (strictures)
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16
Q

What is the commonest cause of MBA?

A 
Nutrition:
-decreased B12/folate in food
OR
-antibodies (pernicious anemia)
OR
-damage to absorptive apparatus in GIT disorders (gastritis, intestinal disorders, chronic gastroenteritis, surgery, IBD, malabsorption syndrome)
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17
Q

How does cancer Tx. cause MBA?

A

many antineoplastic drugs inhibit folate as folate is required for cell division

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18
Q

What is the pathogenesis of MBA?

A

decreased B12/folate –> decreased DNA metabolism –> decreased cell division

*therefore ALL cells in bone marrow decrease in no. (PANCYTOPENIA) –> low RBCs, WBCs, plts

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19
Q

What is the morphology of MBA?

A
  • macrocytic (decreased cell division = increased cell size)
  • oval macrocytes
  • pancytopenia
  • anisopoikilocytosis
  • hypersegmented neutrophils
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20
Q

What are the clinical features of MBA?

A
  • glossitis
  • chelitis
  • stomatitis
  • jaundice (mild) –> hemolysis of large RBCs
  • bruising –> decreased plts
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21
Q

What is anisopoikilocytosis and in which anemia(s) can it be seen?

A
  • variation in size (anisocytosis) and shape (poikilocytosis) of RBCs
  • can be seen in microcytic anemia (IDA)
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22
Q

What is pernicious anemia?

A
  • vit. B12 deficiency due to autoimmune atrophic gastritis in elderly
  • autoantibodies against intrinsic factor (IF) and parietal cells (type I, II, III)
  • therefore decreased absorption of B12
  • decreased tetra-hydrofolate (folic acid)
  • decreased DNA synthesis –> MBA
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23
Q

What are the non-pernicious causes of Vit B12 deficiency?

A
  • gastrectomy
  • achlorhydria (decr. stomach acid)
  • chronic pancreatitis
  • ileal resection
  • malabsorption syndromes
  • tapeworm infestation
  • malignancy, pregnancy, hyperthyroidism
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24
Q

How does Vit. B12 deficiency cause neurological defects and what are they?

A
  • vit B12 necessary for myelin synthesis
  • deficiency –> nerves become demyelinated and dysfunctional (esp. in spinal dorsal tract - sensory tracts)
  • loss of proprioception/peripheral neuropathy
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25
Q

What are the clinical features of pernicious anemia?

A

MBA Sx. + neurological deficits (spinal dorsal tract) –> i.e. loss of proprioception

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26
Q

Which foodgroups contain B12 + folate?

A

B12 –> animals (meat); bacteria (microorganisms)

Folate –> green vegetables

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27
Q

Why are cells microcytic in IDA?

A
  • DNA is normal
  • Hb is decreased (therefore cytoplasm maturation is delayed)
    • therefore cells continue to divide resulting in microcytic, hypochromic RBCs
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28
Q

What is the etiology of ACD?

A
  • chronic infections
  • inflammations
  • malignancy
  • anemia of renal disease (decr. EPO)
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29
Q

What is the pathogenesis of ACD?

A
  • IFN-gamma, TNF-alpha, IL-1/6 + elevated hepcidin levels all inhibit iron transfer from macrophages/reticuloendothelial system to RBCs
  • decreased EPO = decreased RBC production
  • increased hemophagocytosis by macrophages
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30
Q

What is the morphology of ACD?

A

-mild microcytic, hypochromic

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31
Q

What are the clinical features of ACD?

A
  • mild anemia

- NO response to iron Tx.

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32
Q

How is ACD diagnosed and why will it not respond to iron therapy?

A

Iron studies
-serum ferritin will by normal/high (whereas it will be decreased in IDA)

*No response to iron Tx. as there is already an ample amount of iron present already which is just being inhibited from being released from macrophages

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33
Q

What is aplastic anemia and what are the causes?

A

BM failure

–> stem cell damage (drugs, immune, viral infections - HBV)

34
Q

What is the morphology and clinical features of aplastic anemia?

A

Morphology:
-normocytic, pancytopenia

CF’s:

  • low RBCs –> anemia
  • low WBCs –> infections
  • low plts –> bleeding
35
Q

True or false?

Hepcidin is increased in ACD

A

True

-hepcidin inhibits iron release from reticuloendothelial system

36
Q

What is the commonest hemolytic anemia?

A

Acquired

-immune AIHA (warm/cold)

37
Q

What is the normal lifespan of RBCs?

A

120days

38
Q

What occurs as a result of increased RBC destruction?

A
  • increased bilirubin –> jaundice (unconjugated hyperbilirubinemia)
  • increased RBC production (compensatory) –> BM hyperplasia + increased reticulocytes
39
Q

What are the features of acute + chronic hemolytic anemia?

A

Acute:

  • pallor
  • jaundice (normal urine) –> unconjugated bilirubin

Chronic:

  • splenomegaly
  • pigment gall stones
  • BM hyperplasia
  • ?hepatomegaly
40
Q

What is intravascular and extravascular hemolysis?

A

Intravascular:
-RBCs broken down INSIDE blood vessel

Extravascular:

  • RBCs broken down OUTSIDE blood vessel
  • in liver or spleen
41
Q

What is responsible for normal urine colour?

A

conjugated bilirubin

-conjugated in liver

42
Q

What is released when RBCs undergo hemolysis and what occurs consequentially?

A

Globins/Iron –> recycled
Porphyrin –> unconjugated bilirubin –> liver for conjugation –> conjugated bilirubin –> urine

*if marked hemolysis, liver cannot handle all the unconj. bilirubin –> jaundice

43
Q

What is the pathogenesis of jaundice in hemolytic anemia?

A

increased RBC breakdown –> increased porphyrin release –> unconjugated hyperbilirubinemia

*liver cannot handle all of the unconj. bilirubin for conjugation –> so excess unconj. bilirubin gets shunted to blood –> jaundice

44
Q

What is the etiology of intravascular hemolysis?

A
  • immune HA (esp. cold)
  • mechanical
  • enzyme deficiencies (G6PD)
  • transfusion mismatch (mistake)
  • drugs
  • infections –> DIC, malaria
45
Q

What serum globin handles released Hb from intravascular hemolysis, and what occurs when there is markedly elevated Hb released?

A

Haptoglobin (Hp)

  • forms Hp/Hb complex
  • converted to heme –> unconjugated bilirubin –> liver –> conjugation –> biliary system

*if Hb markedly elevated from increased intravascular hemolysis –> haptoglobins are LOST
THEREFORE, increased Hb dimers leading to:
-hemoglobinemia
-hemoglobinuria
-hemosiderinuria
—> RENAL FAILURE :(

46
Q

What is found on lab Dx. of intravascular hemolysis, and what are the clinical features?

A

Lab Dx.

  • absent haptoglobins
  • hemoglobinemia
  • hemoglobinuria
  • hemosiderinuria
  • these are toxic to kidneys –> clinical features thus consist of shock and renal failure
47
Q

What is present in extravascular hemolysis?

A
  • safe handling of dead RBCs by liver + spleen
  • unconjugated hyperbilirubinemia ONLY
  • kidneys are protected :)
48
Q

What happens to WBC/Plt count in hemolytic anemia?

A

Both increase

-in response to the breakdown of RBCs which usually evokes an inflammatory response

49
Q

What is the morphology of hemolytic anemia?

A

Abnormal RBC shapes

  • spherocytes in WIHA
  • target cells in thalassemia

Polychromatophils
-immature RBC –> large, bluish, no central pallor –> reticulocytes

Nucleated RBC severe cases)
-small nucleus inside reticulocyte (v. immature)

50
Q

When might you see target cells on a blood film?

A

thalassemia

51
Q

What stain can you use in hemolytic anemias?

A

Methylene blue stain for cytoplasmic RNA

–> present in reticulocytes which are likely to be elevated in hemolytic anemia

52
Q

What does reticulocytosis suggest?

A

Increased RBC production

53
Q

Compare IgG to IgM

A

IgG:

  • monomer, small
  • coats RBC with no complement activation (weak Ab)
  • WARM - commonest; sticks better at body temp
  • predominantly extravascular

IgM:

  • pentamer, large
  • activates complement, causes clumping and lysis of RBCs (strong Ab)
  • COLD
  • predominantly intravascular
  • increases with infections
54
Q

What is the cause and pathogenesis of AIHA (IgG + IgM)?

A 
Cause: - RBC antibody (commonest)
Pathogenesis:
*warm/IgG
-coated RBC lysis in spleen
-drugs, idiopathic
-predominantly extravascular
-spherocytes
  • cold/IgM
  • infections, lymphoma
  • RBC agglutination + complement fixation (C3b) lysis in BV + liver
  • predominantly intravascular
55
Q

What is the morphology of WIHA + CIHA?

A

Warm:
-spherocytes (due to gradual loss of membrane from splenic macrophages due to coated IgG Abs)

Cold:
-RBC clumps/agglutination (IgM pentamers)

56
Q

What Dx. test is used for AIHA and describe it?

A 
Coombs Test --> indirect and direct
Direct (do 1st):
-for Ag on pts. RBC
-pts. RBC incubated with anti-human Abs to IgG/C3
-agglutination = + test

Indirect:

  • for Abs in pts. serum
  • pts. serum incubated with RBCs
  • binding of any IgG to reagent RBCs
  • incubation with anti-human Abs to IgG
  • agglutination = + test
57
Q

What are schistocytes and when are they seen?

A

Fragmented/broken RBCs

  • seen in microangipathic hemolytic anemia (MAHA)
  • fibrin threads in BV in DIC slice RBC membrane –> schistocytes
58
Q

What is the commonest etiology of mechanical damage causing MAHA?

A

DIC:
-fibrin threads slice RBC membrane forming schistocytes

also:
-TTP/HUS –> thrombi formation in BVs
-valve disease/artificial valves (i.e. stenosis)
march hemoglobinuria –> RBC damage in foot capillaries (heavy exercisers/long-walkers –> army)

59
Q

What is the morphology of microangiopathic hemolytic anemia (MAHA)?

A

Fragmented RBCs –> schistocytes

Polychromasia –> reticulocytes (in response to increased damage to RBCs)

60
Q

What is the commonest membrane cytoskeleton deficiency in herditary spherocytosis?

A

Spectrin deficiency

61
Q

True or False?

WAHA has > spherocytes than hereditary spherocytosis

A

FALSE

62
Q

Why is there massive splenomegaly in hereditary spherocytosis?

A

-lots of spherocyte RBC breakdown by splenic macrophages –> splenomegaly

63
Q

Is hereditary spherocytosis coombs test pos. or neg.?

A

negative (it is NOT an autoimmune condition)

64
Q

What is responsible for oxidative damage in G6PD deficiency?

A
  • lack of conversion of H2O2 –> H20

- high H2O2 levels –> oxidative damage

65
Q

What are Heinz bodies?

A

Inclusions within RBCs composed of abnormal/denatured globins as a result of oxidative damage in G6PD deficiency

66
Q

What are bite + blister cells?

A
  • result of G6PD deficiency
  • “dry RBCs”
  • due to lack of H2O –> Hb becomes solid
67
Q

What are the consequences of G6PD deficiency?

A
  1. G6PD deficiency
  2. oxidative damage
  3. heinz bodies (denatured globins)
  4. bite + blister cells (dry RBCs)
  5. episodic hemolysis
  6. splenomegaly; gall stones (pigment stones)
68
Q

What is HbF?

A
  • fetal hemoglobin (75%) - gamma chain
  • increased O2 affinity (absorbs increased O2 from placenta)
  • decreased ability to release O2 –> therefore after birth need HbA (alpha/beta chain) which are more efficient at releasing O2
69
Q

What is physiologic anemia?

A
  • 6 month period after birth there is destruction of HbF and conversion to HbA
  • therefore resultant PHYSIOLOGICAL ANEMIA
70
Q

What globin chains constitute HbF and HbA?

A

HbF –> 2 alpha + 2 gamma chains

HbA –> 2 alpha + 2 beta chains

71
Q

What are the 2 categories of congenital Hb disorders?

A
  1. Qualitative (e.g. sickle cell anemia)
    - abnormal globin chain
    - hemoglobinopathy
  2. Quantitative (e.g. thalassemia)
    - normal globin chain
    - decreased no. of either one of the globin chains
72
Q

What is Hb Barts?

A

Hb Barts has 4 beta chains

-therefore pts will have alpha-thalassemia as there is low alpha chains and only beta chains are forming hemoglobin

73
Q

What does a child with HbS have?

A

sickle cell anemia

74
Q

What are the 2 morphological abnormalities in beta-thalassemia?

A
  1. Heinz bodies
    - from insoluble alpha-globin aggregate
  2. basophilic stippling
    (3. target cells)???
75
Q

What are the features of thalassemia?

A
  • decreased normal Hb –> micro/hypochromic
  • increased destruction –> hemolysis
  • BM hyperplasia –> skeletal deformities
  • increased iron (systemic iron overload) –> secondary hemochromatosis
76
Q

What mutation is responsible for sickle cell anemia?

A
  • beta-chain of HbA is affected
  • at position 6 there is a POINT MUTATION that transforms glutamic acid –> valine
  • HbA –> HbS
77
Q

What is sickle cell crisis?

A
  • sickle-shaped/curved RBCs are sticky + hard and dont flow easily
  • they can get stuck in small BVs of chest (ACS), belly, joints, BM, spleen, etc –> sickle cell crisis
78
Q

What are the common clinical features amongst all types of hemolytic anemias?

A
  • anemia
  • jaundice
  • pigment gall stones
79
Q

What are the clinical features of sickle cell disease?

A
  • anemia
  • jaundice
  • pigment gall stones
  • leg ulcers*
  • auto-splenectomy*
  • crisis*
  • = due to capillary blocks
80
Q

What are the causes of relative or spurious erythrocytosis in polycythemia?

A

Dehydration

  • diarrhoea
  • vomiting
  • diuretics
  • increased alcohol consumption
  • etc.
81
Q

What are the causes of secondary absolute erythrocytosis (true)?

A

Tissue hypoxia

  • smoking (CO binds irreversibly to Hb –> decr. tissue oxygenation)
  • high altitude
  • lung disease (COPD)
  • cardiac shunts (R–>L)

High O2 affinity Hb
-HbF

High EPO

  • paraneoplastic syndromes
  • androgen therapy
82
Q

What is polycythemia rubra vera?

A

Primary absolute (true) erythrocytosis

  • myeloproliferative disorder (MPD)
  • neoplastic proliferation of erythroid cells in BM
  • usually seen in old age (v. red skin/flushed)
  • hepatosplenomegaly

Pathology Term 3 (6 decks)

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