RED BLOOD CELLS (Rbcs, Erythrocytes, Corpuscles)

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RED BLOOD CELLS (RBCs, erythrocytes, corpuscles)

Male / Female
Hgb normal
anemia / 13.5-17.5
˂13.5 / 11.5-15.5
˂11.5
RBC count (106/uL) / 4.5-6.5 / 3.9-5.6
MCV (mean corpuscular volume) / 80-95 is normocytic
MCHC (mean corpuscular Hgb [ ]) / 32-34 is normochromic

a.  RBC production requires protein/lipid/nucleotides (B12 and folate)/glucose/Fe+2 (heme)

i.  If folate or B12 deficient, NO nucleotide interconversion so cells are large w/ lots RNA and protein but can’t divide so undergo intramedullary hemolysis→ ↑MCV/marrow Fe and ↓Hgb/WBC/platelets/retics

ii.  If Fe is deficient, Hgb synthesis can’t occur and cells can’t progress past basophilic normoblast stage

iii. Reticulocyte Count is marker for RBC production and is normally 1-2%/d

-  With acute condition may see ↑ to 4-6%/d

-  With chronic condition may see ↑ to ˃15%/d

iv. As RBC maturation progresses, cell size ↓ and chromatin condenses prior to nuclear exclusion

b.  Intrinsic causes of RBC destruction:

i.  Hemoglobinopathies

ii.  RBC membrane defects (hereditary spherocytosis where everything is either a microspherocyte or a retic; hereditary elliptocytosis due to a spectrin defect; hereditary stomatocytosis)

iii. Poor G6PD activity resulting in Hgb oxidation (see Bite cells and Blister cells)

iv. Poor pyruvate kinase activity resulting in lack of reducing equivalents needed to produce energy

c.  Extrinsic causes of RBC destruction:

i.  AI hemolytic anemia (IgG or complement on the RBC; Fc receptors on MØ in spleen)

ii.  Vascular damage/RBC damage due to toxins

iii. Myelofibrosis or overgrowth of another cell type crowds out BM

d.  Stages in RBC development (takes 4d and is controlled by erythropoietin from kidney):

Erythroblast

↓

Basophilic Normoblast

↓

Polychromatophilic Normoblast

↓

Orthochromatophilic Normoblast

↓

Nucleated RBC

↓

Reticulocyte (contains RNA) or Polychromatophilic Cell

↓

Mature RBC (~120d lifespan)

Anisocytosis = cells are varied sizes (↑RDW)

Poikilocytosis = odd-looking cells (such as no central pallor)

Dacrocyte = teardrop RBC

Spherocyte = small RBC w/ no central pallor

Burr cell = No central pallor and appear to have many pseudopods extending from membrane surface

Acanthocyte =

Schistocyte/Helmet cell = fragmented RBC (due to vascular damage where fibrin bands in vessels shear RBCs)

e.  BM diseases fit into 3 broad categories:

i.  2° to systemic disease

ii.  1° disorder of blood cell production/function (non-cancer)

iii. Clonal hematopoietic disorders (cancer) described next page

-  Chronic myeloproliferative disorders: stem cells acquire genetic defect →clonal expansion of 1+ non-lymphoid blood elements (↑production but normal maturation); see splenomegaly; may progress to acute leukemia

-  Myelodysplastic disorders: stem cells acquire a genetic defect resulting in structural abnormalities/ premature cell destruction (see peripheral cytopenia w/ abnormal cells including classic pseudo Pelger-Huet PMNs w/ bi-lobed nuclei and hypercellular BM)

-  Acute Leukemia: acquired defects → clonal expansion w/o much maturation beyond blast stage in BM

f.  Other tidbits:

i.  Along w/ mature cells, small amt of retics and bands normally released into blood

ii.  Differentiation into specific type of granulocyte occurs at the myelocyte stage where specific secondary granules appear

iii. Vit/mineral defcy = low retic (<100,000 in anemia pt) vs increased RBC destruction = high retic (tries to replace lost cells)

iv. Phago = monos (anything), neutros (bacteria) via Fc/C3b “handle”. Chemokines/APC by monos.

v.  Chronic Granulomatous Dz = XRec, defective respiratory burst → recurrent infxns

vi. Platelets are non-nucleated fragments of megakaryocytes that contain mRNA; live 8-10d (first 1-2d spent in spleen)

ANEMIA CLASSIFICATION

1.  Low Hgb = <13.5 in M, <11.5 in F. Due to blood loss, ↓ production of RBCs, inefficient hematopoesis, ↑ destruction of RBCs

2.  Microcytic- most common type of anemia (aka HCMC or hypochromic microcytic)

a.  Iron deficienicy (most common- 85% of all anemias)→see detail below on iron deficiency anemia

i.  Almost always due to blood loss in adults; may be due to nutritional deficiency in kids 3mo-3yr old

ii.  Hgb synth: Fe2+ is put into heme group, surrounded by α & β globin chains

iii. Basophilic normoblasts are 1st to incorporate Fe2+ due to ↑ receptor density

iv. If Fe2+ becomes limiting, no progression past basophilic normoblast stage

v.  You will see: ↑↑Basophilic normoblasts in marrow, ↓MCV (50s), ↓reticulocytes (in normal range), and of course low Fe2+

b.  Anemia of chronic disease, late stage (rarely)=Sideropenic anemia w/ reticuloendothelial siderosis (SARS)

c.  Thalassemias

d.  Sideroblastic Anemia

e.  Lead poisoning

3.  Macrocytic

a.  Megaloblastic- Myeloid to Erythroid ratio in bone marrow should be 3:1 and is more like 1:1 (erythroid hyperplasia)

i.  B12 (cobalamin) deficiency “Pale Yellow” (absorbed in ilieum)- Dx PA w/ Schilling Test (is B12 absorption ↑ if give GIF?)

1.  Due to ↓ absorption (pernicious anemia (PA)= lose parietal cells that make GIF) or ↑ need (i.e. preg, neoplasms, hyperthyroid)

2.  Slow onset/large stores (yrs), body adapts à severe anemia + neuro Sx (from AdoCbl) such as wide-based gait due to loss of vibratory and positional senses and neuropathy/dementia

3.  Fxn: adenosylcobalamin (AdoCbl) converts CH3-malonyl-CoAà Suc-CoA & methylcobalamin involves CH3-transferase and B9

ii.  B9 (folate) deficiency “How Dry I Am”

1.  Due to poor diet w/o green leafy veg (EtOH), ↑ need (preg, infants), impairment (MTX, DNA (-))

2.  Quick onset/small stores (last few months), no neuro Sx

3.  Important for dUMP to dTMP (thymidylate synthase)

iii. bothà no nucleotide interconversion, plenty of RNA/protein with little/no DNAà RNA/DNA mismatchàintramedullary hemolysis

iv. Smear=macro-ovalocytes, hypersegmented neutrophils, giant megakaryocytes = megalo-erythroblasts

v.  You see: ↑MCV (120s), ↓↓Hgb, ↓WBC, ↓platelet, very low reticulocytes, ↑marrow Fe (b/c it isn’t used), ↑LDH/bilirubin

vi. Tx = B12 IM, folate PO, always check both, as folate can mask anemia caused by B12 w/o fixing neurologic problems

b.  Liver disease/cirrhosis (large stomatocytes/target cells due to poor lipid handling in liver such that RBCs pick up lipid as they pass through liver and add it to their membranes)

4.  Normocytic (aka NCNC or normochromic normocytic)

a.  Reticulocyte count <3%

i.  acute blood loss (takes 7 days to form new retics)

ii.  early stage iron loss

iii. early stage anemia of chronic disease

iv. aplastic anemia (BM can’t make cells – often due to chemo, can be infection, genetic)

v.  renal disease (↓EPO synthesis)

b.  Reticulocyte count >3%

i.  Intrinsic RBC defect

1.  Hemolytic anemias (membrane abnormalities)

a.  Hereditary spherocytosis (spectrin/ankyrin binding defect)

b.  Hereditary elliptocytosis (spectrin defect)

c.  Paroxysmal nocturnal hemoglobinuria

2.  Hemoglobinopathies (abnormal Hgb)

a.  Sickle cell disease (HbS)

b.  HbC

c.  Thalessemia

3.  G6PD deficiency (enzyme defcy)- RBC not protected from Hb oxidation

4.  Pyruvate Kinase Deficiency- RBC w/ poor energy production for pumps

ii.  Extrinsic RBC defect (“extracorpuscular”) à ↑RBC loss

1.  Chronic blood loss

2.  Autoimmune hemolytic anemias (Ig or complement on the RBC)

3.  Vascular damage w/ damage to RBC: hemolytic toxins

4.  Microangiopathic hemolytic anemia (DIC)

5.  Myelofibrosis (hematopoietic stem cells crowded out by fibrosis)

6.  Myelopthisis (hematopoietic stem cells crowded out by cancer cells that have spread to bone marrow)

7.  Infection: Mycoplasma, Mono, Malaria

8.  Trauma

microcytic / normocytic / macrocytic
Fe2+ deficiency / aplastic anemia / megablastic
thalassemia / myelopthisis / liver disease
sideroblastic anemia / anemia of chronic disease (ACD) / cirrhosis
Pb poisoning / hypothyroid
ACD / mixed: micro and macro

5.  Shapes of cells:

a.  Membrane defects: Spherocytes (small/no central pallor), Burr Cells, Acanthocytes (irregular burr cells), Stomatocytes, and target cells

b.  Due to Trauma: Schistocyte (broken up), Dadrocytes (teardrop), bite/blister cells

Iron Deficiency Anemias

1.  Almost always due to blood loss, only diet related if pediatric (seen w/in 3 months to 3 years)

2.  Iron stores/RE cell stores lost first, then transferrin, Hgb, and enzyme iron (iron in muscle Mgb not participating in body pool)

3.  Transport and storage iron involves three main substances: transferrin, transferrin receptors, and ferritin

4.  Transferrin (represents the TIBC or total iron binding capacity, TIBC saturation is normally ˃25%)

a.  β globulin serum protein (free iron is toxic and requires a chaperone in blood) that binds two Fe2+ and releases it to needy cells

b.  Picks Fe up from GI mucosal cells, reticuloendothelial (RE) cells, hepatocytes via ferroportin receptor (basal)

c.  Nucleated RBCs take up Fe2+ from transferrin old RBCs are ingested by RE cells where Hgb is digested to release Fe2+ which is outsourced to transferrin or stored as ferritin

d.  Transferrin w/o iron can bind to cells that have receptors that become ferroportins that allow transferrin to extract up to 2 iron molecules from the cell (mucosal cells/RE cells/hepatocytes have ferroportins)

e.  If transferrin saturated, Fe2+ accumulates in endocrine glands, pancreas, heart hepatocytes leading to organ damage/hemochromatosis

5.  Ferritin

a.  Water soluble iron-protein complex made-up of protein shell and a Fe-PO4-OH core

b.  If serum ferritin is normal in anemic pt, you know it isn’t due to Fe deficiency b/c serum Fe is directly correlated to ferritin level

c.  Storage form of Fe2+ (thus ↑ in iron overload, unlike transferrin receptor which is down-reg)

d.  Hemosiderin is water insoluble iron storage form made of partially digested ferritin

e.  When iron loss exceeds absorption, stores deplete 1st and completely before anemia develops

6.  Hepcidin: ↓ Fe2+ absorption by dampening ferroportin

7.  Iron Absorption (iron level is controlled via modulation of intake/absorption as there is no way to ↑ excretion in overload)

a.  Occurs in duodenum and jejunum

b.  Mucosal cell is programmed to absorb a certain percent from lumen, set by HFE (hemochromatosis gene) in base of crypts

c.  HFE sets activity of ferroportin, which provides attachment of transferrin and Fe2+ uptake

d.  Divalent Metal ion Transfer protein (DMT-1)on luminal surface allows iron (and other +2 ions) into mucosal cells/RE cells and its activity is inversely related to iron levels/ferritin content of these cells

e.  Ferric form (Fe3+) is in food and needs stabilization w/ gastric acid or reduction for absorption ferrous (Fe2+) form is stable/absorbed

8.  Anemia develops first as microcytic and later becomes hypochromic

9.  Clinical Presentation = pallor, painless glossitis, angular stomatitis (cracks/sores @ corners of mouth), pica, spoon nails (koilonichia)

10.  Labs = MCV <80, ↓MCHC, low serum ferritin, low serum Fe low TIBC saturation (˂10%) (but not necessary to test if low ferritin)

11.  Smear = enlarged central pallor, anisocytosis with microcytes

Anemia of Chronic Disease (or SARS)

1.  Second most common cause of anemia accounting for 15% of all anemic patients

2.  Underlying disorder does not have to be chronic (pneumonia is #1 cause), but cell death does have to be part of the disease process

3.  Labs = Hgb rarely 8 gm/dl w/ normal or ↑ serum ferritin, low serum Fe and TIBC 10-25%, Prussian blue stain of marrow is positive

4.  Smear= usually normocytic, normochromic (NCNC) but may be hypochromic (rarely microcytic)

5.  Reticulocyte count w/in normal range, but lower than one would expect if bone marrow were trying to keep up due to:

a.  Shortened RBC life (40-80 days)

b.  Failure of EPO (erythropoietin) response to anemia

i.  Stays same as when RBCs have normal life-span

ii.  Thought to be due to cytokine factors involved in tissue injury, including TNF and IL-1

6.  Shift of iron from Hgb to stores (thus anemic but normal/↑ ferritin)

7.  Bone Marrow shows low sideroblast count (iron-containing nucleated RBCs)→sideropenic anemia while RE iron is normal or ↑→RE siderosis

8.  Treat underlying chronic disease

a.  Supplementing w/ Fe won’t work

b.  EPO would ↑Hgb levels but not necessary if treat underlying disease

Sideroblastic Anemias

1.  Inherited X-linked recessive (rare)

2.  Or aqcuired due to:

a.  Myelodysplastic disorder(Refractive Anemia w/ Ringed Sideroblasts (RARS))

b.  Secondary to malignant disease

c.  Due to drugs (chloramphenacol), or toxins (EtOH/Pb2+)

3.  Failure to form heme even though iron is availableàiron accum in mitochondria, seen as granules around nucleus “ringed sideroblast”

Iron overload (Hemosiderosis)

1.  HFE (autosomal recessive)-missense mutations of hemochromatosis gene that controls ferroportin àexcess uptake of Fe2+

2.  Hemosiderosis(state of being iron overloaded)àhemochromatosis(organ damage due to Fe2+ excess)

a.  1° Hemochromatosis: inherited autosomal recessive (HFE)

b.  2° Hemochromatosis is more common: due to excessive transfusions or 2° to chronic hemolytic disease (thals, PK deficiency)

c.  Fe2+ accumulation leads to dysfunction/hemochromatosis:

i.  endocrine glands/pancreasà gonadal dysfunction/DM

ii.  heartà cardiomyopathy

iii. hepatocytesà cirrhosis

iv. hyperpigmentation and arthropathy

3.  Treatment is blood letting

GRANULOCYTES AND MONOCYTES

1.  Granulocytogenesis

a.  Same scheme for all granulocytes (PMNs, eosinophils, and basophils); fate determined at myelocyte stage when specific granules appear

b.  Only segmented neutrophils and bands appear in the blood. Earlier precursors seen in various disease states inc. infections/leukemias

c.  Eosinophils have pink granules containing major basic protein and bi-lobed nucleus; ↑ in response to foreign proteins

d.  Basophils have dark blue granules that contain histamine/heparin/hyaluronic acid; ↑ in response to chronic myeloproliferative disorders; common origin w/ mast cells

2.  Neutrophils

a.  Most common of WBCs and blood granulocytes

b.  3-5 lobed nucleus

c.  Two types of granules:

i.  Primary granules-contain myeloperoxidase

ii.  Secondary granules-contain lysozyme

d.  Digest bacteria/cell debris

e.  Mature in BM over 12-13d

f.  Live ~12h in circulation but can live days in tissue

PMN as example of Granulocytogenesis

3.  Myeloblasts: earliest recognizable of bone marrow precursors

a.  Very large nucleus w/ fine chromatin and 2-5 nucleoli

b.  Cytoplasm is light blue and has no granules

c.  Normal bone marrow contains 0-4% myeloblasts

4.  Promyelocytes: produced by myeloblast cell division

a.  Very large cells w/ abundant cytoplasm, nucleus is similar to myeloblast