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****MS 2 Unit 2 Pathology > Red Blood Cell Disorders > Flashcards

Red Blood Cell Disorders Flashcards

1
Q

Anemia-> definition and classifications

A
  • reduction in circulating RBC mass
  • measured by <b>Hb, Hct & RBC count</b>

Hb <b> in males (N= 13.5-17.5) & <b> in females (N= 12.5-16)</b></b>

*based on MCV (um^3)–> <b>Microcytic (100)</b></b></b>

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2
Q

Microcytic Anemia Overview

A
  • decreased production of Hb
  • extra division of RBC progenitor cells to maintain Hb concentration

*<b>iron deficiency anemia, anemia of chronic disease, sideroblasic anemia & thalassemia</b>

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3
Q

What is Hb & how does heme get into the system?

A

Hb–> 4 hemes–> each made up of protophorphyrin ring–> Fe in center–> binds oxygen

  1. <b>Ferroportin</b>- transports heme from duodeum to blood
  2. <b>Transferrin</b>- transports iron in blood to liver & marrow macrophages for storage
  3. <b>Ferritin</b>: binds intracellular iron preventing the formation of free radicals
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4
Q

Iron Deficiency Anemia–> causes, stages, clinical features, labs, treatment

A
  • <b>dietary lack</b> (malabsorption, malnutrition, gastrectomy) <b>or blood loss</b> (ulcer, menorrhagia, pregnancy, colon polyps/carcinoma, hookworm)
  • stages: depletion of storage iron (low ferritin, high TIBC)–> depletion of serum iron (low % saturation)–> normocytic anemia–> microcytic, hypochromic anemia
  • Clinical Features: anemia, koilonychia, pica

<b>-labs: microcytic, hypochromic RBCs, high RDW (red cell distribution width), low ferritin, serum iron & % saturation, high TIBC & free erythrocyte protoporphyrin (FEP)</b>

-treatment: ferrous sulfate (iron supplement)

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5
Q

lab tests

A
  • serum iron: iron in blood
  • TIBC: measures transferrin
  • % saturation: % of transferrin molecules bound by iron
  • serrum ferritin: reflects stores in macrophages and liver
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6
Q

Plummer-Vinson Syndrome

A

-iron-deficiency anemia with <b>esophageal web and atrophic glossitis</b> presenting as anemia, dysphagia and beefy-red tongue

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7
Q

Anemia of Chronic Disease–> cause, Hepcidin’s role, labs

A

-from chronic inflammation leading to production of acute phase reactants from liver (i.e. hepcidin)

<i>Hepcidin sequesters iron sites by limiting iron transfer from macrophages to erythroid precursoes & suppressing EPO prduction to prevent bacteria from accessing iron (which they need for survival)</i>

-<b>labs: high ferritin & free erythrocyte protoporphyrin, low TIBC, serum iron & % saturation</b>

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8
Q

Sideroblastic Anemia

A
  • <b>congential or acquired defect in protoporphyrin synthesis</b> causing iron to remain trapped in mitochondria
  • *<b>forms a ring around nucleus of erythroid precursors (ringed sideroblasts)</b>
  • congenital–> ALAS (rate-limiting enzyme)
  • acquired–> alcoholism (damages mitochondria which makes protoporphrin), lead poisoning (inhibits ALAD and ferrochelatase), VB6 deficiency (required cofactor for ALAS)

<b>-labs: high ferritin, serum iron & % saturation, low TIBC</b></b>

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9
Q

Important relationships between labs

A

indirect: ferritin and TIBC
direct: serum iron and % saturation

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10
Q

Protoporphyrin synthesis

A

Succinyl CoA –(ALAS & Vitamin B6 cofactor)–> ALA
ALA –(ALAD)–> Porphobilinogen
Porphobilinogen —-> Protoporphyrin
Protoporphyrin + Fe –(Ferrochelatase)–> Heme

<b>**first reaction is rate-limiting</b>
<i>**final reaction occurs in mitochondria</i>

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11
Q

Thalassemia Overview

A
  • inherited mutation causing decreased synthesis of a or B globin chains <b>(normal Hb: HbF (a2y2), HbA (a2B2), HbA2 (a2d2))</b>
  • carriers are protected against <b>Plasmodium falciparum malaria</b>
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12
Q

a Thalassemia

A

-gene deletion:

1= asymptomatic
2= mild anemia with increased RBC count (cis- severe and in Asians, trans- Africans)
3= severe anemia <b>(B chains form tetramers HbH that damage RBCs)</b>
4= hydrops fetalis; <b>(y chains form tetramers HbBarts that damage RBCs)</b>
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13
Q

B Thalassemia

A
  • gene mutations (African or Mediterranean descent):
  • chrmosome 11 which has two B genes

<b>Minor</b>: mild, asymptomatic, increased RBC count, microcytic hypochromic RBCs & target cells; decreased HbA and increased HbA2 & HbF

<b>Major</b>: severe, high HbF is temporarily protective, unpaired a chains precipitate and damage RBC membrane (ineffective erythropoiesis & extravascular hemolysis), <b>massive erythroid hyperplasia</b> (expansion of hematopoiesis into skull and facial bones, extramedullary hematopoiesis with hepatosplenomegaly and risk of aplastic crisis with parvovirus B19 infecton of erythroid precursors); microcutic, hypochromic RBCs with target cells and nucleated RBCs; no HbA

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14
Q

Macrocytic Anemia Overview

A

-commonly due to folate or VB12 deficiency (megaloblastic anemia) which impairs DNA precursor synthesis

  • <b>Megaloblastic anemia</b>- from impaired division & RBC enlargement
  • <b>Hypersegmented neutrophils</b>- from impaired division of granulocytic precursors
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15
Q

Folate deficiency (Macrocytic Anemia)

A
  • folate is absorbed in the <b>jejunum</b>
  • <i>minimal body stores</i>
  • causes: poor diet, increased demand (pregnancy, cancer, hemolytic anemia), & folate antagonists

-<b>labs: macrocytic RBCs & hypersegmented neutrophils, glossitis, low serum folate, high serum homocysteine (not converted to methionine), normal methylmalonic acid</b>

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16
Q

Vitamin B12 deficiency (Macrocytic Anemia)

A
  • takes years to develop due to <i>large hepatic stores</i>
  • most commonly caused by <b>pernicious anemia</b> (autoimmune destruction of parietal cells); or pancreatic insufficiency and damage to terminal ileum

<b>-labs: macrocytic RBCs & hypersegmented neutrophils, glossitis, <i>spinal cord degeneration</i>, low serum VB12, high serum homocysteine & <i>methylmalonic acid</i></b>

<i>VB12 is a cofactor for conversion of methylmalonic acid to succinyl CoA. With a deficiency, methlmalonic acid accumulates and impairs spinal cord myelination leading to poorproprioception and vibratory sensation and spastic paresis</i></b>

17
Q

Normal Vitamin B12 movement throughout the body

A
  • VB12 is liberated from animal proteins by salivary gland enzymes and carried to stomach by R-binder
  • pancreatic proteins detach VB12 from R-binder
  • VB12 binds intrinsic factor (from parietal cells) which is absorbed in the ileum
18
Q

Normocytic Anemia Overview

A
  • normal-sized RBCs

- <b>increased peripheral destruction or underproduction</b> distinguished by reticulocyte count

19
Q

Reticulocytes

A
  • young RBCs= large, blueish cytoplasm (residual RNA)
  • Normally 1-2% which replaces RBCs that die after 120 days but increases to 3% in response to anemia

<b>**RC is falsely elevated in anemia since is it measured as a percentage of total RBCs
**corrected by: Rc x Hct/45</b>

20
Q

Peripheral RBC Destruction (Hemolysis)

A

-extravascular or intravascular resulting in anemia with good marrow response

<b>Extravascular</b>: (hereditary spherocytosis, sickle cell anemia) RBC destruction by reticuloendothelial system (macrophages consume them); anemia with splenomegaly, jaundice, risk for bilirubin gallstones, marrow hyperplasia with corrected RC >3%

<b>Intravascular</b>: (PNH, G6PD, IHA, microangiopathic hemolytic anemia, malaria) RBC destruction within vessels; hemoglobinemia, hemoglobinuria, hemosiderinuria, decreased serum haptoglobin

  • <i>haptoglobin usually binds Hb to reprocess in spleen</i>
  • hemosiderinuria: shedding of tubular cells after an accumulation of hemosiderin (Hb broken down into iron)</i>
21
Q

How do macrophages break down Hb?

A

globin–> amino acids

heme–> iron (recycled) & protoporphyrin

protoporphyrin–> unconjugated bilirubin (bound to albumin & delivered to liver for conjugation & excretion into bile)

22
Q

Hereditary Spherocytosis–> cause, labs, diagnosis, treatment

A
  • defect of RBC cytoskeleton-membrane tethering proteins (ankyrin, spectin, band 3)
  • formation of blebs and spherocytes (round cells)

<b>-spherocytes are less able to get through splenic sinusoids and thus are consumed by macrophages</b>

-<b>labs: spherocytes with loss of central pallor, high RDW & MCHC, splenomegaly, jaundice, risk of gallstones, aplastic crisis with parvovirus B19 infection of erythroid precursors</b>

<i>diagnosed with osmotic fragility test & treated with splenectomy (treats anemia but results in spherocytes and Howell-Jolly bodies</i>

23
Q

Sickle Cell Anemia–> trait and disease

A

-mutation of B chain (glu–>val) but driven by hypoxemia, dehydration & acidosis

<b>Sickle Cell Disease–> 2 abnormal B genes</b>
-<b>deoxygenated HbS polymerizes–> aggregate into needle-like structures</b>

-sickle and de-sickle causing RBC membrane damage and <b>complications of vaso-occlusion</b>: dactylitis (edema), autosplenectomy (leading to increased risk of infection by encapsulated organisms), acute chest syndrome, pain crisis, renal papillary necrosis (hematuria & proteinuria)

<b>Sickle Cell Trait–> 1 abnormal B gene</b>

  • asymptomatic with no anemia
  • renal medulla- sickling with hypoxia and hypertonicity
24
Q

Hemoglobin C

A
  • AR mutation in B chain (glu–>lys)
  • <b>mild anemia due to extravascular hemolysis</b>
  • HbC crystals</b>
25
Q

Paroxysmal Nocturnal Hemoglobinuria (PNH)

A

Cause: acquired defect in myeloid stem cells–> absent GPI–> cells susceptible to destruction by complement

<i>GPI secures DAF to the membrane
DAF inhibits C3 convertase (protecting against complement-mediated damage)</i>

Clinical features: episodic intravascular hemolysis (thus hemoglobinemia & hemoglobinuria; hemosiderinuria) during sleep since complement is activated by respiratory acidosis–> platelet fragments can induce thromosis

<b>test: sucrose test for screening, acidified serum test of flow cytometry to detect lack of CD55 (DAF) on blood cells is confirmatory test</b>

Complications: iron deficiency anemia & AML

26
Q

Glucose-6-Phosphate Dehydrogenase Deficiency (G6PD)

A

-reduced G6PD half life increasing susceptibility to oxidative stress

<b>low G6PD–> low NADPH–> low reduced glutatione–> oxidative injury by H2O2 (causing Hb precipitation as Heinz bodies which become bite cells when removed by macrophages)–> intravascular hemolysis</b>

-African (mild) & Mediterranean (severe) variants: protective role against <b>falciparum malaria</b>

27
Q

Immune Hemolytic Anemia (IHA)

A

-Ab mediated (IgG or IgM) destruction of RBCs

<b>IgG-mediated</b>: extravascular hemolysis; associated with SLE, CLL and certain drugs

<b>IgM</b>: intravascular hemolysis; RBCs inactivate complement but residual C3b serves as an opsonin for spenic macrophages resulting in spherocytes and <b>associated with Mycoplasma pneumoniae and infectious mononucleosis</b>

  • Coombs tests diagnoses IHA (direct or indirect)
  • <b>direct</b>: agglutination occurs if RBCs are already coated with IgG or complement when anti-IgG-complement is added
  • <b>indirect</b>: agglutination occurs if serum Ab are present when anti-IgG and test RBCs are added
28
Q

Microangiopathic Hemolytic Anemia

A
  • vascular pathology causing destruction of RBCs (intravascular hemolysis)
  • occurs with microthrombi: TPP-HUS, DIC, HELLP, prosthetic heart valves & aortic stenosis <b>producing schistocytes on blood smear</b>
29
Q

Malaria

A
  • infection of RBCs and liver with Plasmodium (transmitted by female Anopheles mosquito)
  • <b>RBCs rupture; intravascular hemolysis and cyclical fever</b>
  • P. falciparum- daily fever
  • P. vivax & P. ovale- fever every other day

-<i>mile extravascular hemolysis with splenomegaly since spleen consumes some RBCs</i>

30
Q

Anemia due to under production Overview

A
  • decreased RBC production by marrow
  • low corrected RC
  • <b>etiologies: causes of microcytic & macrocytic anemia (low RC), renal failure (low EPO), damage to bone marrow precursors (progenitor cells do not develop properly)</b>
31
Q

Parvovirus B19

A
  • infection of progenitor red cells halting erythropoiesis–> significant anemia in setting of preexisiting marrow stress
  • infection is self-limited
32
Q

Aplastic Anemia

A
  • pancytopenia with low RC due to damage to hematopoietic stem cells
  • due to: drugs, chemicals, viral infections, autoimmune damage

<b>biopsy</b>–> empty, fatty marrow

  • treatment: marrow stimulating factors (erythropoietin, GM-CSF, G-CSF), transfusions, bone marrow transplantation
  • <i>immunosuppression may be helpful as some idiopathic cases are due to abnormal T-cell activation with release of cytokines</i>
33
Q

Myelophthisic Process

A
  • replaces bone marrow

- hematopoiesis is impaired–> <b>pancytopenia</b>

****MS 2 Unit 2 Pathology (4 decks)

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