Two of the most challenging and commonly encountered immune-mediated diseases in small animal practice are immune-mediated hemolytic anemia (IMHA) and immune-mediated thrombocytopenia (ITP).
IMHA is a condition in which the body's own immune system mistakenly targets and destroys its red blood cells, leading to potentially life-threatening anemia. ITP follows a similar principle but, instead of red blood cells, the immune system attacks and destroys platelets — the cells responsible for normal blood clotting — leaving patients at serious risk of spontaneous bleeding. Both conditions are considered primary or idiopathic when no underlying cause can be identified. Secondary or associative forms can be triggered by infections, certain medications, cancer, or other immune stimuli.
These are not rare diseases. IMHA is one of the most common causes of severe anemia in dogs, and both IMHA and ITP rank among the top reasons for referral to internal medicine and emergency and critical care specialists. Dogs are affected far more commonly than cats, with young to middle-aged, female dogs most commonly affected. While any breed can be affected, Cocker Spaniels, Springer Spaniels and Poodles have been overrepresented in the literature. Despite advances in treatment, IMHA carries a mortality rate as high as 50 to 75%, underscoring just how serious these diseases are and why getting treatment right from the start matters so much! Learn more on Mastering IMHA in Dogs.
With that context in mind, here are five practical tips and reminders that can help to maximize the likelihood of successfully managing dogs with IMHA and ITP:
- Regarding the use of antibiotics — avoid treating these patients with cephalosporins and sulfa drugs. These drug categories can trigger immune reactions in patients and, potentially, cause a relapse of autoimmune disease. It's important to remember — even several years down the road — to avoid using these medications in a patient that has a history of IMHA or ITP.
- Take a thoughtful, individualized approach to vaccination. The thinking and recommendations about vaccination are continually evolving. Current evidence no longer supports a blanket "no vaccines ever" policy for patients in remission from IMHA or ITP. A 2024 study1 found that vaccine administration after diagnosis was not statistically associated with disease relapse in dogs with IMHA, ITP, or immune-mediated polyarthritis. That said, many still advise against vaccinating any patient with active immune-mediated disease and, if vaccination is warranted, always defer until remission is achieved and clinical signs are well controlled.
Do not label every IMHA or ITP patient as one that should never be vaccinated. Once a patient is in remission, the decision to vaccinate should be made on a case-by-case basis — weighing the likelihood of relapse, the potential severity if relapse occurs, and the patient's realistic risk of exposure to infectious disease. For many patients, titer testing is still a practical and reasonable strategy — annual titers for core vaccines, and a rabies titer if the client needs to demonstrate immunity to a boarding or grooming facility. Veterinarians should have a conversation and involve the client in making the decision. Always document the risk-benefit discussion and decision about vaccination in the patient's medical record.
- Adjunct immunosuppressive therapy is very commonly used along with prednisone as a mainstay of treatment. The most common adjunct drugs used include cyclosporine at a dose of 5 mg/kg by mouth every 12 hours, or mycophenolate at a dose of 8-12 mg/kg by mouth every 12 hours. Azathioprine at 2 mg/kg PO q24h is another well-established option recognized in the most current ACVIM guidelines2. These steroid-sparing agents are great to use in conjunction with prednisone to facilitate a quicker taper of prednisone over the first three to four months — with the secondary immunosuppressive drug continuing to provide coverage and hopefully preventing relapse.
Wean immunosuppressive therapy slowly - starting with a taper of the glucocorticoids. Typically this means reducing drug dosages by 20 to 25% each month after a pet achieves remission. It's also advisable not to juggle medications during the first month of disease — after a patient is diagnosed and discharged from its initial hospitalization, consider waiting at least one month before making any changes. Many also recommend running a CBC seven days after any dose reduction, to ensure that the patient is not showing indication of relapse.
- Be thoughtful and targeted with the use of GI protectants. Omeprazole (a proton pump inhibitor (PPI)) remains the most efficacious acid suppressant — it outperforms famotidine in studies and, when GI protection is indicated, is a strong choice at 1 mg/kg PO q12h.
However, as indicated in the 2018 ACVIM consensus statement on GI protectants3, routine prophylactic use of proton pump inhibitors is not appropriate for every patient. Current guidelines recommend GI protection specifically for patients with risk factors for ulceration — such as high-dose corticosteroid therapy, concurrent NSAID use, or clinical GI signs. Prescribing omeprazole by default without a clear indication is considered overprescribing, and long-term unnecessary PPI use can carry its own risks including GI dysbiosis.
There are also possible drug interactions to be aware of if the IMHA patient is on mycophenolate or clopidogrel (an antiplatelet drug). Antithrombotics are indicated in dogs with IMHA except for those with severe thrombocytopenia. The 2018 ACVIM consensus regarding the use of GI protectants3 states that, although direct evidence is lacking in dogs and cats, there is compelling evidence in humans that PPIs should not be concurrently administered with other drugs that require an acid environment for oral absorption – which include mycophenylate and clopidogrel. Additionally, omeprazole inhibits the CYP2C19 enzyme and can reduce the antiplatelet activation of clopidogrel. In those patients, pantoprazole or famotidine may be safer alternatives for GI protection.
- Finally, don't panic about leukocytosis. An elevated white blood cell count is very common in these patients, particularly within the first month or two of disease recovery. Remember that bone marrow regeneration is not selective in our veterinary patients — once the patient's red blood cells or platelets start to rebound, so will the white blood cells. This elevation most likely does not correlate with infection. Only start antibiotics if the patient has a fever or clinical evidence or indicators of infection. More specifically, if you have a confirmed or suspected infection in a patient, strongly consider culture and sensitivity testing — the majority of these patients are still significantly immunosuppressed, and we should be providing antibiotic support based on culture results whenever possible. Remember to avoid cephalosporins and sulfa drugs - if indicated, a safer option for patients with immune-mediated disease is enrofloxacin.
References:
- Comparison of timing of relapse in dogs with nonassociative immune-mediated hemolytic anemia, thrombocytopenia, or polyarthritis. J Vet Intern Med. March-April 2024;38(2):1035–1042. doi: 10.1111/jvim.17004
- ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs. J Vet Intern Med. May-June 2019;33(3):1141-1172. doi: 10.1111/jvim.15463
- ACVIM consensus statement: Support for rational administration of gastrointestinal protectants to dogs and cats. J Vet Intern Med. 2018 Oct 31;32(6):1823–1840. doi: 10.1111/jvim.15337
×
