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Immunology > IMHA > Flashcards

IMHA Flashcards

1
Q

IMHA

A
  • Life threatening
  • Common in dogs and rare in cats
  • Characterised by type II immune reaction where RBCs coated with immunoglobulin, complement or both are removed from circulation bu direct destruction or phagocytosis
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2
Q

Primary IMHA

A
  • Idiopathic
  • autoimmune hemolytic anemia
  • true autoimmune reaction against self antigen on erythrocytes
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3
Q

Secondary IMHA

A
  • associated with presence of a foreign antigen
  • stimulates immune system to destroy erythrocytes without a true autoantibody
  • triggers: systemic infections, drugs and neoplasia
  • more common than primary in cats
  • non immune mediated : direct RBC destruction from disorders such as Dirofilaria immitis infection and vena-caval syndrome (hemolysis occur due to trauma to the RBCs when they circulate through parasite thrombus)
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4
Q

What kind of dogs and cats are predisposed to IMHA?

A

Female dogs and male cats

Average age of 6.5years for dogs and 3 years for cats

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5
Q

Signs and symptoms of IMHA

A

*Lethargy, depression, anorexia for 3 days or more, discoloured urine, vomiting, diarrhoea, dyspnea,

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6
Q

Seasonal component to IMHA

A

Spring and summer

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7
Q

Initial physical exam findings

A

Pallor, tachycardia, fever, icterus, cranial organomegaly, lymphadenopathy, petechiae

Cats: hypothermic

Systolic heart murmur, hyper dynamic pulse quality, dyspnea, collapse

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8
Q

PCV in IMHA patient

A

Less than 25% and as low as 6%

Spherocytosis common in 85-95% of cases (difficult to identify in cats due to size)

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9
Q

Signs of regeneration

A

Polychromasia, anisocytosis, macrocytosis, nucleated RBCs, reticulocytes

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10
Q

Nonregenerative anaemia

A
  • found in up to 50% of dogs and most cats at presentation

* dogs take 3-5 days while cats take 7 days to regenerate

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11
Q

Thrombocytopenia

A

*occur in 50-70% of dogs and rare in cats

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12
Q

Combination of thrombocytopenia and hemolytic anaemia

A

Evan’s syndrome

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13
Q

Serum biochemical adnormalities

A

Total bilirunin elevation, hepatic transaminase and alkaline phosphatase elevation, azotemia, and hyperglobulinemia.

Urinalysis shows bilirubinuria or hemoglobinuria

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14
Q

DIC

A

Prolonged coagulation times (prothrombin time, activated partial thromboplastin time) and increased fibrin degradation products and d-dimers are consistent with DIC

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15
Q

What test is used to diagnose IMHA?

A

Spontaneous macroagglutination on slide agglutination test is diagnostic when rouleaux formation has been ruled out by saline washing

  • Not all dogs will hav autoagglutination
  • Macroagglutination is not diagnostic of IMHA in cats
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16
Q

How is slide agglutination test performed ?

A
  • one drop of EDTA-blood on a glass slide and gently mixing with one drop of saline
  • slide is gently rocked while being observed for clumping of RBCs (macroagglutination)
17
Q

Coomb’s test

A
  • direct antiglobulin test (DAT)
  • used to detect anti-erythrocyte antibody or complement on the surface of RBCs
  • Mixing of anticoagulated patient RBCs with rabbit or goat anti-canine (or anti-feline) immunoglobulin or complement which reacts with immunoglobulin or complement-coated RBC to result in aglgutination
  • positive in 35-60% of dogs with IMHA
  • can produce false positive and negative results
18
Q

Treatment for IMHA

A
  • no single best treatment
  • supportive care to treat anemia - IVF crystalloids
  • minimise risk of secondary complications
  • immunosuppresive drug therapy - Glucocorticoids: prednisolone PO, dex IV if PO not tolerated
  • potentially secondary immunosuppressive drugs: azathioprine and cyclosporine
  • potential blood transfusion: packed RBCs over whole blood
  • less volume
  • less chance of reaction to plasma proteins
19
Q

What is the risk of IV catherization in patients with IMHA?

A

It increases the risk of pulmonary thromboembolism

-the most common cause of death for dogs with IMHA

20
Q

How do you determine when to transfuse an IMHA patient?

A

Based on presence of clinical signs of weakness, tachycardia, tachypnea, rapidly decreasing PCV

21
Q

Drawbacks of transfusion therapy

A
  • suppression of erythropoietin response
  • prolongation of time to erythroid recovery
  • possibly increased risk of pulmonary thromboembolism
  • presence of autoantibodies may shorten survival of transfused red cells
22
Q

Complications of IMHA

A
  • Thromboembolism
  • indicative of patient in hypercoagulable state
  • risk factors for development of thrombophilia and thromboembolism
  • blood stasis
  • hypercoagulability
  • vascular endothelial injury
  • hyperbilirubinemia
  • hypoalbuminemia
  • severe thrombocytopenia
23
Q

Where is the most common location of clinically evident thromboembolism?

A

The pulmonary system

-cerebral thromboembolism can also occur

24
Q

Clinical signs of thromboembolism in the pulmonary system?

A 
Acute respiratory difficulty
Orthopnea
Profound anorexia
Acute neurologic decompensation 
Neuro-lateralizing signs 
Sudden death
25
Q

What anticoagulant therapy can you use to treat suspected hypercoagulability associated with IMHA?

A

Heparin require antithrombin to be effective and antithrombin is decreased in dogs with IMHA- hence not an effective anticoagulant

Immunology (3 decks)

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