Abnormalities of the Erythron Flashcards
In which animals are RBCs nucleated?
Reptiles and birds
Which animals have elliptical RBCs?
Camelids
Where are the sites of RBC production?
Foetus - Liver and spleen Neonates - Bone marrow Growing animals - Bone marrow of all bones Long bones - red/yellow marrow Flat bones - remain active
Liver and spleen maintain erythropoietic capacity.
What is required for the production of RBCs?
Stem cells Space in the marrow Growth factors Iron Cholesterol/lipids Enzymes
How does the nucleus and cytoplasm change during RBC maturation? What are the stage?
- Rubriblast
- Prorubicyte
- Basophillic rubricyte
- Polychromataphilic rubricyte
- Metarubricyte
- Reticulocyte
As the cell matures the nucleus becomes more clumpy. Cytoplasm goes from dark to light blue, to orange
Nucleus is then extruded and becomes reticulocytes, which mature to erythrocyte.
What is the life span of erythrocytes in:
a. Dog
b. Cat
c. Horse, cattle
a. 100 days
b. 70 days
c. 150 days
How are RBCs usually removed?
Major route = senescent red cells taken up by phagocytic macrophages, components recycled.
Minor route = intravascular haemolysis
What is evidence for reduction in red cell mass on biochemistry?
Decreased:
- Haemoglobin concentration [Hgb]
- PCV
- Haemtocrit
- Red blood cell concentration [RBC]
What is haemtocrit?
Same as PCV but calculated. Relies on red cell count and volume. Less accurate.
What leads to decreased red cell mass?
Increased loss
Decreased production
What are the classes of anaemia?
Mild, moderate, severe
Regenerative vs non-regenerative
Normocytic, microcytic, macrocytic
Normochromic, hypochromic, hyperchromic
Describe mild anaemia…
Just below - 10% below normal PCV
May not affect animals until exercised
Common in animals with longstanding disease e.g. endocrine
Describe moderate anaemia…
May show weakness or be well adapted.
MM pallor, fast bounding pulses
Slow drop = easy to cope with
Fast drop - easily affected and weak
Describe severe anaemia…
PCV in lower teens downwards
Pale, weak, unable to exercise
May ned oxygen stabilisation before diagnostics
Don’t fight anaemic cats!
What is the difference between MCH and MCHC?
MCH = (g) Content MCHC = (g/dL) per volume of fluid i.e. bigger cells needs more haemoglobin
What does a hypochromic red blood cell indicate?
Iron deficiency/poor iron incorporation (with microcytosis)
Central pallor increases
Describe normocytic anaemia..
Erythrocyte of unremarkable size
Often associated with mild non-regenerative anaemia, acute haemorrhage
Describe macrocytic anaemia…
Regeneration - polychromatophils larger than mature RBCs
Seen in poodles
99% macrocytic are regenerative and also hypochromic
Describe microcytic anaemia…
Red cell haemoglobin concentration determinds when division stops
Iron deficiency allows an extra division
PSS, Fe, hepatic failure and akitas
If a cell is very pale, they are very thin.
When is macrocytosis of RBCs seen?
Regenerative anaemia
FeLV affected cats
In myelodysplasia
Artefact in stored blood
How does the body respond to a fall in oxygen tension?
- Kidneys respond to low blood O2 by releasing erythropoietin
- Stimulates bone marrows to increase RBC production
- Takes 2-3 days and younger cells increase in circulation
If it is regenerative, what are the potential causes of anaemia?
Haemorrhage
Haemolysis
What is the reticulocyte %?
1000 cells counted, reticulocytes expressed as a %
What is the corrected reticulocyte %?
Same number of reticulocytes will take up more % in a very anaemic animal
Reticulocyte % x patient PCV/normal PCV
When is the corrected reticulocyte % indicative of regeneration?
When it is >1% in dogs and >0.4% in cats.
What is the absolute reticulocyte concentration?
[RBC] x Retic %
Causes of external haemorrhage that increases loss of RBCs…
Melena
Urinary tract
Epistaxis
Post-trauma/surgery
Describe melena…
Digested blood in faeces
GI ulceration/neoplasia - gradual loss of blood not always visible
Iron lost forever!
Causes of internal haemorrhage that increases losses of RBCs…
Bleeding tumours Trauma Into tissues Surgery Body will breakdown RBC outside of vessels and resorb iron
Causes of haemolysis that increases loss of RBCs
Increased internal RBC destruction
Intravascular/extravascular
Normal erythrocyte damage
Describe IMHA…
Immune mediated haemolytic anaemia
Anti RBC antibodies - IgG/M/A
Red cells opsonised and either lysed or phagocytosed
May aggultinate
Coomb’s test positive for anti-RBC antibody
May be severe/rapid usually strongly regenerative
What does RBC agglutination look like on a smear?
Strong bond of RBCs through antibodies
Grape-like clusters that look like flakes grossly
What is rouleaux? What does it look like on a smear?
Normal, especially in horses
High protein +ve charge stopes RBCs repelling each other
Looks like stacked coins
How can you distinguish agglutination from rouleaux?
Add saline - the lower the drop in protein conc (dilatation) the less cells will clump together with rouleaux.
How can you test for RBC agglutination?
In saline agglutination test
One drop of saline and one drop of EDTA mixed on a slide
Looks like flecking before it starts to dry if +ve
What are ghost cells?
What are they indicative of?
Remnants of RBCs that have lost haemoglobin
Complement pokes holes in RBCs and haemoglobin leaks into plasma - a hallmark of intravascular haemolysis
Red/pink plasma
Membrane only
What are spherocytes?
What are they indicative of?
Round, dark and dense cell with no central pallor
99% certain it is IMHA
Extravascular haemolysis - macrophages bite chunks out of RBCs and if it survives it becomes spherocyte.
What lab findings are associated with IMHA?
Regenerative anaemia
Increased bilirubin
Neutrophilia, monocytosis
Platelets may be affected
Which parasites cause haemolysis?
Mycoplasma haemofelis and M. maemominutum
Blood borne and increases fragility and haemolysis
Either destroys the cell itself or immune system destroys cell because of parasite
Babesia
What does mycoplasma haemofelis look like on a smear?
Small rings on red blood cell surface
How can you diagnose mycoplasma haemofelis?
PCR - gold standard
Blood smear
What are heinz bodies?
Are cats or dogs more susceptible?
Denatured haemoglobin
Due to oxidative damage e.g. onions, paracetamol, vit K, propylene glycol
Cats >dogs
Low numbers is normal in cats
What are eccentrocytes?
Haemoglobin has uneven distribution within the RBC
Oxidative damage to membrane
Dogs >cats
Horses with red maple toxicosis
What does it mean if you see lots of eccentrocytes?
Damage has occurred recently/occuring now because they are quickly removed from the circulation
What are the products of shear injury?
Shistocytes
Keratocytes
Accompany microangipathic damage (vasculitis/tumours narrowing vessels) as causes RBC damage when passes through
What are acanthocytes?
Uneven surface projection from RBCs
Associated with splenic disease e.g. haemangiosarcoma
What are keratocytes?
RBC with apposed and sealed membrane
Helmet shaped
Associated with shearing e.g. DIC, vasculitis
Seen with schistocytes
What are schistocytes?
RBC fragments occur secondary to shear injury
Associated with fibrin deposition in vessels and DIC
What inherited diseases cause abnormal RBCs?
Pyruvate kinases deficiency
- Chronic
- Severe haemolysis
- Initially regenerative the myelofibrosis and die 1year
- Basenjis and beagles
Phosphdructokinase deficiency
- RBC sensitive to alkaline pH
- Low grade haemolysis with severe episodes
- Springers
What is the most common cause of non-regenerative anaemia?
Anaemia due to inflammatory/chronic disease.
Describe the usual presentation of anaemia of chronic disease….
Non-regenerative
Normocytic, normochromic
Mild, slow progressing
Fe sequestration, inflammatory mediators, shortened erythrocyte survival
Describe renal non-regenerative anaemia…
Decreased erythropoeitin production
Normocytic, normochromic
Impacts QOL
How can you treat renal non-regenerative anaemia?
Erythropoietin injections available but may develop Ab and wipe out own erythropoietin
Aim to increase PCV, not back to normal
Describe endocrine non-regenerative anaemia…
Hypothyroidism and hypoadrenocorticism
Normocytic, normochromic
Mild
Thyroid hormone and cortisol facultative effect on RBC production
Describe non-regenerative anaemia caused by FeLV
70% of anaemic cats Selective depression of erythropoeiesis Dysplasia production Myeloproliferative disease vrowding out Normochromic normocytic but many are macrocytic
Describe non-regenerative marrow…
What can cause it?
All precursors wiped out (aplasia anaemia)
Fat, plasma cells, mast cells left
Need core biopsy
Causes: FeLV Oestrogen toxicity Phenylbutazone Chemotherpay Unknown
What is myelodysplasia? What would you see in the marrow?
Adequate cellularity in marrow but abnormal maturation/production of cells
Marrow: Erythrocyte macrocytosis Binucleate Maturation defects Giant neutrophils Hyper segmented neutrophiles Macroplatelets May go onto leukaemia
What is the difference between leukaemia and myelodysplasia?
Leukaemia - lots of cells produced that enter the bloodstream
Myelodysplasia - lots of abnormal cells produced that don’t survive in the blood stream
Why do neoplastic conditions of the bone marrow causes anaemia?
Non-regenerative due to crowding of the bone marrow
Altered environment
Usually haemopoeitic neoplasms
What is myelofibrosis?
Fibrosis of the bone marrow = response to injury
Osteosclerosis - cortical bone increases
May get marked extra-medullary haematopoiesis
When does iron deficiency anaemia become non-regenerative?
Chronic cases - bone marrow runs out of iron (can usually cope for a few months)
When does immune mediated anaemia become non-regenerative?
Immune mediated attack on precusors, non peripheral RBCs
What is erythrocytosis (polycythemia)?
Increases in HCT, RBC count and haemoglobin
What are the causes of erythrocytosis (polycythemia)?
Splenic contraction
Neoplasm
Dehydration
Increase production e.g. altitude/neoplasm
Describe primary erythrocytosis…
Myeloproliferative disorder or erythroid stem cells
EPO normal or decreased
PO2 normal
Describe secondary erythrocytosis
Appropriate or inappropriate
Chronic hypoxia e.g. altitude
EPO secreting tumours
EPO levels elevated
