Immune Diseases - IMHA Flashcards
Everything about Immune Mediated Hemolytic Anemia in small animals
Age predisposition of IMHA of both dogs and cats
Dogs - Middle aged; 6.5yrs avg (13wks-13yrs)
Cats - Young/middle aged; 3yrs (6mths-9yrs)
Any age can be affected
Breed disposition of IMHA
Dogs - 1/3 of all cases are Cocker Spaniels (also Springer, Poodles, OESDs etc.)
Cats - no predispositions
Gender predisposition of IMHA
Dogs - Female
Cats - Male
How does vaccination influence IMHA
25% of dogs had been vaccinated within days of diagnosis in one study
IMHA seasonal incidence?
Spring and summer
Infectious (secondary) causes of RBC destruction in IMHA include
1) Tick-bourne diseases
2) Babesia spp.
3) Dirofilaria immitis
4) Microfilaria
Toxic (secondary) causes of RBC destruction in IMHA include
1) Zinc
2) Acetaminophen
3) Onions/garlic
4) Copper
5) Castor beans
Drug related (secondary) causes of RBC destruction in IMHA include
Penicillin, Cephalosporins, Sulfonamides, Quinidine, Procainamide, Phenothiazines, Methylene blue, Methimazole
Neoplastic (secondary) causes of RBC destruction in IMHA include
Hemolymphatic tumors and Solid tumors
Immune (secondary) causes of RBC destruction in IMHA include
SLE and hypothyroidism
Metabolic (secondary) causes of RBC destruction in IMHA include
Hypophophataemia (severe)
Inherited / intrinsic RBC defects in IMHA include
PFK deficiency and PK deficiency
Explain the pathophysiology of IMHA
Increase in procoagulant activity, decrease in anticoagulant activity, decreased fibrinolysis = Thromboembolism, DIC
Mucous membranes physical exam findings in IMHA
Pale
+/- icteric
+/- petechia/ecchymoses
Temperature physical exam findings in IMHA
Dogs - Pyrexia
Cats - Hypothermia
Pulse physical exam findings in IMHA
Tachycardia
+/- prominent pulses
+/- anemic murmur
Respiratory physical exam findings in IMHA
Tachypnea
+/- respiratory distress
Abdominal palpation physical exam findings in IMHA
Hepatosplenomegly and Abdominal pain
IMHA most common clinical signs
Lethargy, depression, anorexia
IMHA less common clinical signs
Vomiting & Diarrhea PU/PD Weakness Exercise Intolerence Collapse/ syncope Pigmenturia Respiratory distress Pica
CBC results for IMHA
Moderate to severe regenerative anemia Neutrophilic leukocytosis Thrombocytopenia Normal TP (rules out blood loss) Evidence of RBC destruction (spherocytosis, autoagglutionation, +ve Coomb's test)
Describe Saline/ slide agglutination test
1 drop blood + 1-2 drops saline
Agitate gently (rock back & forth)
Check for both micro and macroscopic agglutination
+ve in 40-89% IMHA dogs
Biochemistry results for IMHA
Increase Tbilirubin, ALT
+/- azotemia
Urinanalysis results for IMHA
Bilirubinuria
+/- hemoglobinuria
Imaging results for IMHA
To rule out secondary causes
Thoracic Radio: patchy alveolar opacities, pronounced interstitial pattern, mid pleural effusion (PTE)
Abdominal Ultra: Hepatosplenomegaly, extramedullary hematopoiesis
Bone marrow aspirate / biopsy for IMHA
Non regenerative anemia
Coagulation parameters for IMHA
If DIC present; Increase ACT, PT/PTT etc.
Other test Thromboelastography
Treatment for IMHA
Immunosuppression, reduce risk of thrombosis with anticoagulants and antiplatelet drugs, doxycyline and supportive care
1st line steroids (immunosuppression) for treatment of IMHA
Prednisone (2-4mg/kg/day) PO
Dexamethasone SQ or IV if can’t tolerate PO medications
2nd line steroids (immunosuppression) for treatment of IMHA
Azathioprine, Cyclosporine, Mycophenolate mofetil
Anticoagulants (antithrombotics) used for the treatment of IMHA
Unfractured heparin (UFH) IV or SQ
Low molecular weight heparin (LMWH) SQ
Coumadin/warfarin PO
Require monitoring
Antiplatelet drugs (antithrombotics) used for the treatment of IMHA
Aspirin
Clopidogrel
Doesn’t require monitoring
Supportive treatment for IMHA
Blood transfusion (in severely anemic patients if hemodynamically unstable, required in 70-90% of dogs, PRBCs preferred)
Oxygen therapy
IVF therapy
GI protectants (Antacids - H2 blocker/ proton pump inhibitor/ PG analogue; Sucralfate)
Long term management of IMHA
History, PE, and CBC once to twice until resolution of anemia
Biweekly until tappering of immunosuppressive medications is initiated
Maintenance of immunosuppressive glucocorticoid dose until Hct is stable or rising followed by 25-50% dosage reduction every 2-4wks (withdrawal 3-6mths)
CBC prior to each dosage reduction
Complications in IMHA
Pulmonary thromboembolism (PTE) - most common cause of death in IMHA dogs
IMHA prognosis
Guarded
Dogs - 26-70% mortality; highest in first two weeks after diagnosis. May die suddenly even if anemia has resolved or relapse during treatment.
Cats - 24% mortality
Favorable criteria for IMHA
Response to treatment (rise in Hct within 3-7days)
Response to transfusion
Unfavorable criteria for IMHA
Persistent agglutination despite immunosuppression drug
Thrombocytopenia
Leukocytosis +/- left shift
Use of cyclophosphamide
IMHA vaccine
None
