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Flashcards in Hematology - IMHA Deck (64)
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1

What is the pathogenesis of IMHA?

The immune system produces antibodies that bind to the patient's own RBCs leading to RBC destruction via intravascular and extravascular hemolysis

2

What is the most common form of IMHA (think antibody)?

IgG mediated - where RBCs are destroyed by macrophages in the liver in the spleen (Extravascular)

3

How do spheryocytes form?

When macrophages consume a piece of the RBC membrane and not the entire thing they leave fragments called spherocytes

4

IgM activates complement better than ____ which leads to ______ destruction ultimately resulting in ______ hemolysis.

IgG; intravascular; intravascular

5

What are the three etiologies of icterus?

Pre-hepatic due to hemolysis, hepatic, and post-hepatic due to biliary obstruction

6

How do you differentiate between the etiologies of icterus?

Obtain minimum database of CBC, chemistry panel, and urinalysis

7

Why may a dog with IMHA have a non-regenetative anemia at presentation when it is more commonly associated with regenerative anemia?

Immune attack at the level of the bone marrow OR early disease

8

What test is commonly positive in patients with IMHA?

Saline agglutination test

9

What is agglutination in IMHA patients induced by?

five-armed IgM or large quantities of IgG

10

How do you perform a slide agglutination test?

Mix 4 drops of saline with 1 drop of anticoagulated whole blood on a slide. Gently agitate and then examine for macroagglutination. Look under microscope for microagglutination

11

When evaluating a slide agglutination test, what must you look for that is not agglutination due to IMHA?

Rouleaux formation

12

When should a Coomb's test be performed?

Only if there is negative autoagglutination

13

In an IMHA patient, why would there not be autoagglutination?

The anti-RBC antibody levels are too low to cause agglutination

14

What does the Coomb's test detect?

antibodies or complement attached to RBCs

15

What is a common CBC finding in patients with IMHA?

Very high WBC counts

16

What is a leukemoid response?

Neutrophilic leukocytosis with a left shift

17

What can cause a leukemoid response?

Increased marrow release during strong regenerative RBC response or tissue necrosis

18

Leukocytosis in dogs with IMHA is correlated with _______ ______.

tissue necrosis

19

What platelet abnormality is associated with IMHA patients?

thrombocytopenia

20

Why do patients with IMHA often have thrombocytopenia?

Immune-mediated platelet destruction and disseminated intravascular coagulation (DIC)

21

True or false: There are no consistent chemistry abnormalities with IMHA.

TRUE

22

What does a biochemistry often reflect in patients with IMHA?

dehydration (elevated bilirubin) and hypoxic damage (mild to moderate elevations)

23

If there is no red in a urinalysis in a patient with IMHA, what does that indicate?

there is no intravascular hemolysis

24

True or False: There is a single definitive test for IMHA.

FALSE

25

Diagnosis of IMHA is based on a number of findings. Name them.

Anemia with a HCT of < 25-30%
Evidence of hemolysis
Evidence of antibodies against RBCs
Elimination of underlying causes of anemia
An appropriate response to immunosuppressive therapy

26

What are some hereditary non-immune causes of hemolysis?

Pyruvate kinase deficiency (PK), Phosphofructokinase deficiency (PFK), and hereditary stomatocytosis

27

What are some acquired non-immune causes of hemolysis?

Toxins - zinc, onions, garlic
Hypophosphatemia - diabetic ketoacidosis or refeeding syndrome
Microangiopathic hemolytic anemia - DIC or heartworm disease

28

Primary IMHA is what type of hypersensitivity reaction?

type 2 hypersensitivity reaction

29

What breeds are predisposed to primary IMHA?

Cocker spaniels, Old English Sheepdogs, Poodles, and Dachshunds

30

What is secondary IMHA?

An immune response to nonself antigens that have modified or are associated with normal RBC membranes

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