Immune mediated disease Pt. 2 Flashcards
Feline IMHA: Clinical Presentation - what animals? what type is more common?
- Often young cats
- Secondary IMHA more common than primary
> Underlying infections:
> Mycoplasma hemofelis
> Feline leukemia virus
Feline IMHA hematocrit compared to dogs?
Compared to dogs, usually present with lower hematocrit
Feline IMHA diagnosis - hematocrit, spherocytes, coombs… what type of hemolysis is most common?
Compared to dogs, usually present with lower hematocrit
* Average of 0.12 L/L (normal 0.29-0.45)
* Can be non-regenerative
Spherocytes typically cannot be detected
* Due to feline RBC morphology
Coombs test positive in many cases
Extravascular hemolysis most common
Feline IMHA & FELV - what is the link?
- FeLV is a potential cause of secondary IMHA
- BUT - cats with IMHA can have positive FeLV snap test
> Often a false positive early in disease - If your feline IMHA has a positive FeLV snap, Confirm with another test (often FeLV PCR)
Feline IMHA: Complications
- Overall low rate of complications
- Unlike in dogs, thromboembolic complications rare
Feline IMHA: Treatment
Immunosuppressive treatment:
* Some cats respond to single agent
glucocorticoid
* Adjuvant options: cyclosporine most common
Investigate for underlying disease and treat if possible
* E.g., doxycycline mainstay of treatment if Mycoplasma hemofelis
* Corticosteroid often not required if Mycoplasma
Feline IMHA: Outcome - how long to respond to treatment? long term approach? relapse rate?
- Can take months to respond if non-regenerative anemia
- Long-term approach is similar to dogs
- Gradual tapering of immunosuppressive
therapy - Relapse rate similar to dogs (~15-30%)
Epistaxis, petechiation, ecchymoses lead us to suspect…
- Suspect primary hemostatic defect
Melena points to…
- GI blood loss (primary or secondary)
Pale MM’s most likely cause
- Anemia most likely
can we show the immune mediated response against platelets in IMT? how do we diagnose?
- Unlike IMHA:
> No clinically relevant methods to show immune mediated response against platelets - Diagnosis of exclusion
> Rule out other causes of thrombocytopenia
IMT: Establishing the Diagnosis
- how common? what platelet count we expect? what types are there?
- IMT = most common cause of marked thrombocytopenia in dogs
- Platelet count usually <50,000/uL
* Spontaneous bleeding usually <20,000 - IMT can be primary or secondary
* Similar to IMHA causes
Other Causes of Thrombocytopenia aside from IMT
- Sample error***
> Clot in tube, platelet clumps on blood smear - Bone marrow disease (e.g., neoplasia)
> Lack of production - Infection
> Ehrlichia canis, Anaplasma platys
> Disseminated intravascular coagulation
Breed Associated IMT? what do we see in these cases? what do the cells look like, and numbers?
- Congenital macrothrombocytopenia
- Platelet numbers often 50-100,000
- Circulating platelets larger than normal
- Autosomal trait in CKCS (30-50% in US are affected)
- E.g., Norfolk & Cairn Terriers, many others
IMT: Establishing the Diagnosis
- what must we do first? first tests?
Rule out secondary IMT, other causes of thrombocytopenia
* Testing for tick-borne disease as appropriate for region/travel history
* Examine for systemic disease
> Biochemical profile, UA
> Imaging – thoracic radiographs, abdominal ultrasound
IMT: Treatment
Immunosuppressive therapy
* Corticosteroids
* Majority of dogs: platelets improve to 50-100,000/μL in 1 week
Adjuvant immunosuppressives
* May be indicated if low response to therapy
IMT: Adjunctive treatment with vincristine? what is the mechanism?
- Vinca alkaloid, with action of releasing platelets from bone marrow
- Stimulate platelet production?
- More rapid increase in platelets in one study of IMT when used with prednisone
IMT: Adjunctive treatment with vincristine?
- adverse effects
- Potential for adverse effects
- GI, immunosuppression, soft tissue necrosis if injected outside of vein
IMT: Adjunctive treatment with vincristine?
- what cases is this for?
- Often reserved for more severe cases
- 1 dose given early in therapy while waiting for immunosuppression to work
IMT: Transfusion Therapy
- when would we do this? is it common?
- Replace RBCs if indicated
> Acute blood loss, severe anemia - Platelet transfusions uncommon
> Survival of transfused platelets <1 day
> Indications: uncontrolled or life-threatening hemorrhage
IMT: Other Therapies/Management aside from immunosuppressives, vincristine, transfusion…
- Melatonin?
> Potential immune modulation in people with ITP
> Sometimes used in refractory cases
> Unknown benefit - GI hemorrhage common
> Sucralfate, omeprazole? - Restrict activities
IMT: Prognosis
- how many dogs respond to treatment and how fast? mortality? recurrence rates?
- > 70% dogs will respond within 1 week
Single agent corticosteroid
Combination therapy - Recent studies suggest low (10-15%) mortality
- Reported recurrence rates 9-40%
Diagnosing IMPA (immune mediated polyarthritis)
Nonseptic joint cytology
* Usually non-degenerative neutrophils
* 2 or more joints
* No organisms on cyto/culture negative
Ruling out other causes
Antinuclear antibody titer (ANA)
* If other immune-mediated diseases are present
* Systemic lupus erythematosus
IMPA most common form? what forms are there?
- Non-infectious, non-erosive is most common form
- Primary or secondary
> Primary (idiopathic) common
> Secondary to: - Drugs
- Chronic infections (e.g., endocarditis)
- Neoplasia
- Tick-borne disease
Tick-borne disease & IMPA:
- common in ontario?
- what diseases?
Uncommon in Ontario
Can include:
* Borrelia burgdorferi
* Anaplasma phagocytophilium
Treatment for IMPA? how fast can we see results?
- Prednisone
- Gabapentin prescribed for a week; use if needed
- Marked improvement within 1 day
> Comfortable and walking well
> Return to usual self within ~1 week
IMPA: Treatment
- long term considerations
- Most dogs respond to corticosteroids alone
- Gradually wean over 3-6 months
- Occasionally need other immunosuppressive therapy
- Relapse during or after weaning possible
if a dog is receiving high dose immunisuppressive therapy, should we vaccinate?
- Postpone vaccination in dogs receiving high-dose immunosuppressive therapy
- Interfere with vaccine efficacy
- Theoretical risk of infection with live vaccine
> Live vaccines are modified, therefore infection potential unlikely - Legally cannot recommend against rabies vaccination
- Consider individual’s risk of infectious diseases covered by core & non-core vaccines
- Administer those deemed necessary after risk assessment
In an anemic patient, which of the following results is most suggestive of an immune-mediated reaction against the RBC?
a) Concurrent thrombocytopenia
b) Increased mean cell volume
c) Hyperbilirubinemia
d) Autoagglutination
d) Autoagglutination
Which of the following is most suggestive of INTRAVASCULAR hemolysis in patients with IMHA?
a) Bilirubinuria
b) Hemoglobinuria
c) Pale mucous membranes
d) Splenomegaly
b) Hemoglobinuria
Which of the following medications stimulates platelet release from the bone marrow:
a) Vincristine
b) Cyclosporine
c) Prednisone
d) Azathioprine
a) Vincristine
Hepatotoxicity and pancreatitis are potential adverse effects of which of the following medications:
a) Low-dose aspirin
b) Dexamethasone
c) Azathioprine
d) Cyclosporine
c) Azathioprine
Cytology most consistent with immune-mediated polyarthritis is:
a) Nonseptic, neutrophilic inflammation in ONE joint
b) Nonseptic, neutrophilic inflammation in TWO OR MORE joints
c) Mixed inflammation and bacteria in ONE joint
d) Mixed inflammation and bacteria in TWO OR MORE joints
b) Nonseptic, neutrophilic inflammation in TWO OR MORE joints
Arthrocentesis result for IMP
- Joint fluid is yellow, non-viscous
> (Normal appearance – clear, viscous) - Cytology shows 70% non-degenerate neutrophils
> (Normal <5% neutrophils) - Culture negative for bacteria
