Abnormalities - erythron 1 Flashcards
Outline regeneration
- response to fall in O2 tension
- kidneys produce EPO
- EPO stimulates BM to increase RBC production
- tales 2-3 days, younger RBCs (polychromatophils/ reticulocytes) increase in circulation
What is non-regeneration?
where BM doesn’t respond to EPO the way you’d expect
2 differentials for regenerative anaemia
- haemorrhage
- haemolysis
What are reticulocytes?
= polychromatophils
- stain with New Methylene Blue
- RNA precipitates forming aggregates/ ‘reticulum’: reticulocytes
What are polychromatophils?
= reticulocytes
- DiffQuick or Giemsa
- young cell containing rRNA show up as large blue cells and these are polychromatophils
Describe reticulocytes in cats
- cat retics released as aggregate retics maturing to punctate retics over time
- retic counts should record either aggregate or both
Define reticulocyte %
1000 RBCs counted, the retics expressed as a percentage
Define corrected reticulocyte %
the same number of reticulocytes will take up more of a % in a very anaemic animal
= retic % * (patient PCV/ normal PCV)
- 45% normal dog
- 35% normal cat
Define absolute reticulocyte concentratin
= [RBC] * Retic %
Examples - increased loss
EXTERNAL HAEMORRHAGE - melena (GI bleed) - UT - epistaxis - post-trauma/ sx INTERNAL HAEMORRHAGE - bleeding tumours - trauma - into tissue (bleeding diathesis) - sx
Describe melena
- not always visible
- faecal occult blood is very sensitive but not very specific
- meat free diet (white fish/chicken ok) for 5d before test or WILL be positive
Outline haemolysis
- increased internal RBC destruction
- intravascular/ extravascular
- normal erythrocytes or abnormal / damaged
Describe immune-mediated haemolysis
- anti RBC Ab (IgG, IgM, IgA)
- RBCs opsonised and either lyse (more common with IgM) or are phagocytosed
- may agglutinate
- coomb’s test positive (for anti-RBC Ab)
- may be severe/ rapid, usually strongly regenerative
How can you use corrected reticulocyte % to work out if an anaemia is regenerative in dogs and cats?
- cats: regenerative if >0.4% corrected reticulocyte %
- dogs: regenerative if >1% corrected reticulocyte %
Describe the agglutination test
- screening test
- one drop of saline and one drop of EDTA anticoagulated blood mixed on slide and rocked
- look for flecking before it starts to dry
What can appear like agglutination macroscopically?
- Rouleaux
- these are artefacts (not a problem unless increased protein)
- classic appearance on a slide is like a stack of coins
- by bringing down {protein] with saline dilution, will reduce Rouleaux formation
Describe ghost cells
- remnants of RBCs that have lost Hb
- membrane only
- associated with deposition of complement and INTRAVASCULAR haemolysis
Describe IMHA (extravascular)
- macrophages in spleen/ liver attack RBCs with Ab on.
- complete phagocytosis or partial where RBC membrane fuses with that of macrophage and forms spherocyte (small and dark - d/t much Hb)
Other lab findings of IMHA
- increased bilirubin (esp if extravascular haemolysis)
- may have neutrophilia, monocytosis (marrow upregulation)
- PLTs may als be affected - check carefully
- IMHA + I-M platelet destruction = EVAN’S SYNDROME
Describe haemolysis induced by parasites
- Mycoplasma haemofelis and M. haemominutum (formerly Haemobartonella)
- blood borne
- epiceulla rparasite
- large and small forms
- increases fragility and haemolysis
- cyclical (3-8wks)
Dx - Mycoplasma haemfelis
- PCR excellent
- blood smear exam (unreliable)
Describe Babesia in RBCs
- USA > UK
- tick borne
- 2-4 pyyriform bodies in RBC
- haemolytic
- tx (successful if caught early) = imidocarb
Describe Cytauxzoon felis in RBCs
- southern US
- intracellular parasite
- prominent splenic RBC removal
What is Heinz-body associated anaemia?
- denatured Hb = Heiz body
- cats more vulnerable than dogs
- low #s unremarkable in cats
- oxidative injury: onions, paracetamol, vit K, propylene glycol
What are eccentrocytes?
Species?
- Hb has uneven distribution within the cell (eccentric distribution)
- oxidative damage to membrane
- usually dogs
- horses (red maple toxicosis)
Name 2 RBC shear injury products
- schistocytes
- keratocytes
- acanthocytes
- pre-keratocytes - keratocytes
When do shear injuries accompany?
- microangiopathic damage
- tumours with narrow BVs (e,g. HSA) or organ inflammatory beds (severe hepatitis, DIC) where there is fibrin stranding)
- clue to cause
What is an acanthocyte?
- RBC with surface projections of variable length
- projections are unevenly spaced on RBC surface
- associated with splenic dz (HSA)
What are pre-keratocytes?
- shear injury BC
- RBCs with apposed and sealed membrane
- Helmet shaped cells
- associated with shearing - intravascular trauma (e.g. vasculitis, DIC)
- seen with schistocytes
What are schistocytes?
- RBC fragments that occur secondary t shear injury
- associated with fibrin deposition in vessels
- DIC
Describe pyruvate kinase (PK) deficiency
- Basenjis and Beagles
- chronic, severe haemolysis
- initially v regenerative but may go on to develop myelofibrosis
- die at 1 year
Give 3 examples of non-immune- mediated haemolysis
- PK deficiency
- Phosphofructokinase (PFK) deficiency
- feline porphyria
Describe PFK deficiency
- english springers
- RBCs sensitive to alkaline pH
- low grade haemolysis with severe episodes superimposed
Describe non-regenerative anaemia d/t inflammatory/ chronic dz
- most common non-regenerative
- normocytic, normochromic
- usually mild, slow progressing
- Fe sequestration, inflammatory mediators, shortened erythrocyte survival
Describe non-regenerative anaemia d/t renal
- kidneys produce EPO
- with chronic renal failure, production decreases
- normocytic, normochromic
- mild to moderate
- impacts QoL
- EPO injection available but may develop Abs
- aim to increase PCV but not necessarily to normal
Describe non-regenerative anaemia d/t endocrine causes
- hypothyroid and endocrine
- normocytic, normochromic, mild
- thyroid hormone and cortisol have a facultative effect on RBC production
List causes of non-regenerative anaemia
- inflammatory / chronic dz
- renal
- endocrine
- FeLV
Describe non-regenerative anaemia d/t FeLV infection
- up to 70% anaemic cats
- selective depression of erythropoiesis
- dysplastic production
- myeloproliferative dz crowding out
- usually non-specific erythroid hypoplasia
- may be normocytic, normochromic BUT many macrocytic
- associated with FeLV subgroup C
What is aplastic anaemia?
all precursors wiped out, leaves fat, plasma cells and mast cells
Dx - aplastic anaemia
core biopsy
Causes - non-regenerative marrow
- FeLV (rarer nowadays)
- estrogen toxicity
- phenylbutazone
- chemotherapy
- unknown
What is myelodysplasia?
- adequate cellularity in marrow but abnormal maturation / production of cells (ineffective erythropoiesis)
- Marrow: erythrocyte macrocytosis, binucelates, maturation defects, giant neutrophils, hypersegmented neutrophils, macrroplatelets, may go on to leukaemia
What is myelopthisis?
- non-regenerative
- is neoplasia ‘crowding out’ the BM –> altered environment
- usually haemopoietic neoplasms (especially lymphoid)
What is myelofibrosis?
- often response to injury of fibrous elements of marrow: dry taps. may be reactive following prolonged regenerative attempts
- need core: reticulin stains up the fibrous elements
- osteosclerosis: cortical bone increases
- may get marked extramedullary haematopoiesis
T/F: non-regenerative anaemia may become non-regenerative in the long term
True
T/F: I-M attack against RBC precursors (not peripheral mature RBCs) may give a non-regenerative anaemia
True
How can anaemia be classified?
- mild, moderate, severe
- regenerative or non-regenerative
- macro or microcytic
- hypochromic or normochromic
- specific morphology changes
- sample give answer?
What is erythrocytosis (polycythemia)?
- increase in the HCT, RBC count and Hb
- may be spurious or relative (dehydration = volume contraction OR RBC redistribution = splenic contraction
Types of erythrocytosis (polycythemia)
- PRIMARY (polycythemia vera)
- SECONDARY (appropriate or inappropriate)
Describe primary erythrocytosis
= polycythemia vera
- myeloproliferative disorder or erythroid stem cells
- EPO levels normal or decreased
- PO2 normal
Describe secondary erythrocytosis
- appropriate or inappropriate
- chronic hypoxia
- EPO secreting tumours
- EPO levels elevated
Guidelines for taking smears
- always make a fresh blood smear and submit it with EDTA blood sample to ensure good WBC and RBC morphology is maintained
- store blood in fridge until analysis (slows changes)
- smears should be stored at room temp and not in fridge
Guidelines for taking smears
- always make a fresh blood smear and submit it with EDTA blood sample to ensure good WBC and RBC morphology is maintained
- store blood in fridge until analysis (slows changes)
- smears should be stored at room temp and not in fridge
Describe RBC appearance
- biconcave disk most spp
- central pallor (dogs)
- high SA: volume which allows for deformability
- camelids have elliptical RBCs
- anucleat (mammals), nucleated (birds, reptiles)
RBC production sites
- liver/spleen in foetus
- BM in neonate
- growing animals: marrow of all bones
- red/yellow marrow (femur/ humerus) in long bones, flat bones remain active
- liver and spleen maintain erythropoeitc capacity, especially if increased demand (extramedullary haematopoeisis) as do long bones (reversion to red marrow)
Production requirements - RBCs
- stem cells
- space in marrow (caution tumour)
- growth factors (IL-3, GMCSF, GCSF, EPO)
- Fe
- cholesterol/ lipids (membrane)
- enzyme pathways (construction/ maintenance)
Describe RBC maturation appearance
- early: large nucleus, dark blue cytoplasm (d/t blue dye which is basic binding to the acidic RNA elements)
- older: less RNA/ribosome so less blue and more pink
Eryhtrocyte lifespan:
- dog
- cat
- horse/cattle
- dog: 100d
- cat: 70d
- horse/cattle: 150d
Normal RBC removal
- MAJOR ROUTE: senscent RBCs taken up by phagocytic macrophages, components recycled.
- MINOR ROUTE: intravascular haemolysis
What is anaemia evidenced by?
Reduction in red cell mass, evidenced by: - [Hgb] = PCV - HCT - [RBC]
How do HCT and PCV differ?
- essentially the same but HCT is calculated by machine whereas PCV is manual and red cells are red as a % of column after being centrifuged. HCT relies on red cell count and volume
- benefit of PCV over HCT is that you can assess plasma colour (clear/straw or pink if haemolysed), allows buffy coat assessment (WBCs), TP measurement
Describe mild anaemia
- from just below the normal PCV to approx 10% below
- may not affect animal until exercised
- common in animals with longstanding dz, endocrine disorders etc
- usually these animals won’t present to you with mild anaemia as clinical case. More likely that you will discover the animal has mild anaemia when running minimum database
Describe moderate anaemia
- varies b/w spp, depends on normal PCV for each
- may show weakness, may be well-adapted: takes time
- MM pallor, fast bounding pulse
Describe moderate anaemia
- varies b/w spp, depends on normal PCV for each
- may show weakness, may be well-adapted: takes time
- MM pallor, fast bounding pulse
Describe severe anaemia
- PCV in lower teens downwards
- pale, weak, unable to exercise
- may need O2 and stabilisation before diagnostic procedures - brittle
- don’t fight with very anaemic cats!
What is normochromic/ hypochromic?
- Hg concentration
- MCHC/ MCH on panel
- decreased in Fe deficiency/ poor Fe incorporation (with microcytosis)
- hyperchromic not possible as haemolysis occurs before this point
How do you determine if a cell is micro/normo/macro cytic?
- determine MCV
Describe a normocytic RBC
- erythrocytes of unremarkable size, often associated with mild non-regenerative anaemia, acute haemorrhage etc
Describe microcytic RBCs
- red cell hg concentration determines when division stops - Fe deficiency allows one more division: smaller red cells
- PSS, Fe deficiency, hepatic failure
- Akitas/ japanese dogs (normal variation)
Describe macrocytic RBCs
- in regeneration - polychromatophils are larger than mature RBCs
- some poodles
OTHER CAUSES: - FeLV-affected cats (as virus in BM)
- in myelodysplasia
- common artefact in stored (usually posted) blood
