Common Immune Mediated Diseases

What are the common clinical signs of Immune Mediated Diseases?

Fever, lethargy, anorexia

What tests fall under the emergency test category?

PE, MM/CRT, HR, PCV/TS, Blood smear

What is the order of tests done for an emergency patient?

PE —> MM/CRT and HR

PCV/TS

CBC —> Blood smear, Retics, red cell indices

Bone Marrow

Additional testing

A 7 year old dog is presented with a severe regenerative anemia and babesia organisms are identified on the blood smear. What form of immune mediated disease is this?

Secondary (Babesia is causing infected RBCs)

What characterizes a primary or “non-associative” immune mediated disease?

There is no trigger to the immune system

“autoimmune”

Diagnosis by excluding all secondary triggers

What characterizes a secondary or “associative” immune mediated disease?

Something triggered the immune system to attack

What are common triggers in all immune mediated diseases?

Infectious, inflammatory, drug/toxin, neoplasia

Some IMDs have specific associated triggers

What are the 3 most common targets of immune mediated disease?

RBCs (IMHA), Platelets (IMT or ITP), Synovium (Immune mediated polyarthropathy IMPA)

What 2 IMDs characterize Evan’s Syndrome?

IMHA and IMT/ITP

What do we look for in an infectious IMD?

Vector-borne triggers: test for specific diseases, not “general infectious disease panel” — each immune mediated disease has its known triggers

What do we look for in an inflammatory IMD?

Abdominal ultrasound

If find a mass —> FNA, biopsy

**looking for things!

What do we look for in a drug/toxin/med IMD?

History, will know from client reported history

What are we looking for in a neoplasia IMD?

Thoracic radiographs

Abdominal ultrasound ± FNAs and biopsies

***Looking for a tumor!!

If the patient is stable, what should we try first to treat the IMD?

Treat the trigger/etiology, especially if TBD is suspected/known, or in endemic areas

How should we treat IMDs if patient is unstable?

Immunosuppression, have to knock out the immune system to figure out what is going on otherwise immune system will get in the way

What should be given in hospital for immunosuppression?

IV dexamethasone SP 0.2-0.4 mg/kg IV q24 until eating

What should be given at home for immunosuppression after dex sp given and patient is eating again?

Prednisone/prednisolone 2-4 mg/kg/day

4-6 months, slowly weaning ~25% every 2-4 weeks

Goal —> get them off immunosuppression do not want patient on lifelong steroids

What can you never do once starting a patient on immunosuppressive doses?

You can never stop suddenly

Supplementing steroids creates negative feedback on ACTH —> shrinks the adrenal gland, if stop giving cortisol body cannot trigger making cortisol again on its own

What is the physiological dose of prednisone/prednisolone?

0.1-0.25 mg/kg/day

Would use this in example an Addison’s dog that needs steroids to live

What is the anti-inflammatory dose of prednisone/prednisolone?

0.5-1 mg/kg/day

What is the immunosuppressive dose of prednisone/prednisolone?

2-4 mg/kg/day

Would use this in example a chemotherapy protocol where we need higher doses

What is the first line immunosuppressive drug?

Prednisone/prednisolone

When are secondary immunosuppressive drugs needed?

1. Pred side effects are severe

2. Cannot wean off of pred because of relapse

3. Concurrent disease makes pred bad

4. RARE: need more immunosuppression than pred alone

What are some examples of secondary immunosuppressive drugs?

Cyclosporine, mycophenolate, azathioprine, IVIG

What are the most common AE of prednisone/prednisolone?

PU/PD, polyphagia

What is the general prognosis of all IMDs?

Good, most can be weaned off pred within 6 months

All IMDs have a 10-25% risk of relapse, during immunosuppression wean, or in the future —> if relapse occurs usually can go back up to the last dose of pred, and slow the wean

In what situations can immunosuppression be deadly?

Resistant UTIs or skin infections, toxoplasma in cats

What is the prognosis for IMHA?

50/50, can have many problems

How to prevent relapse of IMDs?

Strict tick control!

Careful selection of future drugs, antibiotics (stop any drug they were previously taking) —> clavamox not good for immune mediated dog

Vaccination?

When should you vaccinate even in an immune mediated disease patient?

Parvo risk, other preventable diseases, rabies laws

When should you not vaccinate an immune mediated patient?

Risk of relapse!

What should be discussed with the owner when putting their pet on prednisone or prednisolone?

Basic info of if they see ____ then this is what they should do about it

Consider giving reliable online sources

What are the to be expected pred side effects?

PU/PD, polyphagia, muscle wasting (iatrogenic cushings)

What are the big deal, tell the vet, but not ER pred side effects?

Early signs of infection: skin, UTI, other signs of infection, increased pu/pd, weight loss

What are the go to the ER pred side effects?

Melena, lethargy, pale mm, not eating, drinking, lethargic (may be signs of serious infection)

For an IMHA diagnosis what are the 5 tests that 2/5 must be positive for?

1. Spherocytes

2. Coombs

3. Autoagglutination (SALT test-saline)

4. Tbili elevation

5. Flow cytometry

Diagnosing IMHA step by step

Is it associative or non-associative?

Thorough history (drugs, recent vax, toxins)

Infectious disease testing based on geography (babesia, mycoplasma)

Imaging (neoplasia, inflamm disease, other causes of hemolysis)

What is the rule of 1/3’s in the prognosis for IMHA?

1. Don’t make it out of hospital

2. Survive long term

3. Relapse; or death from thrombo-embolic disease

What is the biggest complication of IMHA?

Thromboembolic disease

What is the acute treatment for IMHA?

Transfusions, supportive care

Immunosuppression

What is at home treatment for IMHA?

Continue immunosuppression

Treat underlying triggers: tick-borne disease (doxy)

Risk of thromboembolic disease

How can we prevent thromboembolic disease when treating IMHA?

Anti-platelet: clopidogrel, aspirin

Anti-coagulant: heparin, rivaroxaban

What diagnostics should be done when questioning if polyarthropathy is immune mediated?

Diagnostics for the immune mediated disease itself and diagnostics for the associative form, underlying triggers

What are diagnostics for the immune mediated disease itself?

Rule out other differentials: infectious, cancer, OA

Radiographs

Infectious: serology

Is it IMPA? Arthrocentesis (cytol and culture)

What is diagnostics of IMPA?

Sterile inflammation result from an arthocentesis sample

What are diagnostics for the associative form, underlying triggers of IMPA?

Infectious —vector borne disease especially

Inflammatory

Drugs/toxins

Neoplasia

What are the 3 differentials for immune mediated neutropenia?

Increased tissue demand —> look for infections

Decreased production

Increased destruction = immune mediated

Increased tissue demand neutropenia

Infections! increased tissue demand causes neutropenia

Organ by organ: respiratory, urinary, abscesses

What can cause decreased production neutropenia?

Drug associated- sulfa drugs (TMS), chemo, estrogens

Genetic-cyclic neutropenia, hereditary B12 deficiency

Bone marrow diseases

When to refer your IMD patient to a specialist?

When patient needs diagnostics or treatments you don’t have the equipment or training to provide

When owner wants a second opinion

When patients is difficult to diagnose and/or treat

When patient has one disease which makes treating for IMD difficult

What are some examples of breeds predisposed to IMDs?

German Shepards

Beagles

Poodles

Shetland sheepdogs

Spaniels