Immune Mediated Hemolytic Anemia

Question 1

T/F: immune mediated hemolytic anemia can be primary or secondary

Answer 1

True

Question 2

Immune mediated hemolytic anemia is a type ________ hypersensitivity reaction

Answer 2

2

Anti-RBC antibodies formed against RBCs

Question 3

Breeds associated with IMHA?

Answer 3

American Cocker Spaniels
English cocker Spaniels
English springer Spaniels

Cross breeds
English sheepdogs 
Irish setters 
Collies 
Dachshunds 
Labrador retrievers 
Min schauzers

Question 4

Signalment of IMHA?

Answer 4

Female > male

Mean age 6 years

Question 5

Clinical signs associated with IMHA?

Answer 5

Collapse, weakness, lethargy, exercise intolerance

Anorexia, dyspnea, vomiting, and diarrhea
Fever, lymphadenopathy

PU/PD

Tissue hypoxia —> tachypnea, tachycardia and increased CO

Splenomegaly and hepatomegaly
Icterus
Pigmenturia

Question 6

What is the syndrome called when there is IMHA and IHT?

Answer 6

Evans syndrome

Question 7

What other immune mediated diseases can accompany IMHA?

Answer 7

Thrombocytopenia
Systemic lupus erythematosus
Glomerulonephritis
Polyarthritis

Question 8

What are the most common antibody types in IMHA reactions?

Answer 8

IgM and IgG

Question 9

The antibodies target _________ on the RBC in IMHA

Answer 9

Glycophorin

Question 10

Attachment of the antibody to the RBC can cause.. ??

Answer 10

Extravascular hemolysis (IgG) —> splenomegaly and hepatomegaly

Intravascular hemolysis (IgM) —> hemoglobinemia and hemoglobinuria

Intravascular RBC agglutination

Question 11

Pathogenesis of leading to intravascular hemolysis?

Answer 11

IgM attaches to RBC
Complement system activated —> membrane attack complex forms and damages cell membrane

-> hemoglobinemia and hemoglobinuria

Question 12

Pathogenesis of extravascular hemolysis

Answer 12

IgG attaches to RBC

Removal of the affected cell my macrophage-phagocyte system (in liver and spleen)

Question 13

DDX for canine IMHA?

Answer 13

Primary/ idiopathic (50-70%)

Secondary

• infection dz
• neoplasia
• drug
• autoimmune

Autoimmune hemolytic anemia - incompatible blood transfusions

Question 14

DDX for feline IMHA?

Answer 14

Primary/idiopathic (35%)

Secondary

• infection
• neoplasia

Autoimmune hemolytic anemia
-feline neonatal isoerythrolysis (eg type A or AB kitten consumes colostrum from type B cat)

Question 15

When you have IMHA what will you include in your diagnostics to rule out secondary causes?

Answer 15

3view thoracic rads 
Abdominal US
Heartworm antigen test 
PCR - infectious dz 
Fecal exam - hookworm

Question 16

What would you see on a blood smear that would be consistent with IMHA?

Answer 16

Spherocytosis
Recticulocytes
Polychromatic
Anisocytosis

Evidence of parasite
Increased number of normoblast (nucleated RBC)

Left shift neutrophilia

Question 17

How can you determine if agglutination is due to IMHA or if its just clumping?

Answer 17

Saline agglutination test—> 1drop of blood to 10 drops saline

Coombs test (direct agglutination test) —> looks for autoantibodies against RBC

Question 18

What is the osmotic fragility test?

Answer 18

Take blood sample, centrifuge RBC
Take 5 drops of RBC into two tubes

Tube 1 —> add 5ml 0.9% saline
Tube 2 —> add 5ml 0.55% saline

If tube 2 is red after 5 min you have membrane fragility

85-100% of dogs with IMHA are postive OFT

Question 19

What will you see in biochem and UA with IMHA?

Answer 19

Biochem - hyperbilibrubinemia

UA

• bilirubinuria
• hemoglobinuria

Question 20

IMHA will cause what changes with thromboelastography?

Answer 20

Lower median clot formation time

Higher median angle
Higher max amplitude
Higher median clot strength

=> hyper-coagulable

Question 21

Why do bone marrow cytology with IMHA?

Answer 21

Evaluate for evidence of myeloid dysplasia

Usually have erythroid proliferation

Occasionally chronic cases could get myeloid fibrosis
Severe hypoxia can damage bone marrow

Question 22

What evidence would point to hypercoagulabilty in an IMHA ?

Answer 22

Hyperfibronogenemia
Antithrombin deficiency
Increased FDPs
Thromboelastography

Question 23

IMHA treatment

Answer 23

Packed RBC
Crystalloid or colloid or both

Immunosuppression - pred is best can have azathioprine

Question 24

How many ml of packed RBC do you want to give to your 18kg canine IMHA patient with a PCV of 12%

Answer 24

Amount (ml) = (PCVreq - PCVpaitent) / PCVblood x body weight x k

K in dogs = 90
PCV of packed PBC = 7%

PCVreq = usually want to bring patient up to 20% PCV

(20-12)/70 x 18kg x 90 = 300mL

Question 25

What is the universal donor for dogs?

Answer 25

DEA 4

Question 26

What is the most common blood type in cats

Answer 26

A

Question 27

What is the best immunosuppressive therapy for IMHA?

Answer 27

Prednisolone

2mg/kg TWICE daily

In combo with Azathioprine

Question 28

What other second line therapies can you combine with pred for IMHA treatment ?

Answer 28

Cyclosporine

Mycophenolate mofetil

Question 29

How would you prevent coagulopathy in IMHA dogs?

Answer 29

Low dose aspirin therapy — inhibit COX 1 on platelet

Clopidogrel — inhibit ADP receptor on platelet membrane

Unfractionated heparin

Question 30

What are the prognostic indicators for Primary IMHA?

Answer 30

Poorer if…
elevated BUN/urea
Elevated FDP, prolonged aPTT, thrombocytopenia
Severe anemia
Higher bilirubin level on day 1
Hypoalbuminemia (hepatopathy)
Inflammatory left shift neutrophillia and monocytosis

Question 31

Mortality rate for primary IMHA?

Answer 31

52%

About 65-75% survive the first year -> progressive hemolysis and organ failure —> DIC or thromboembolism