🩸 Vet-Approved Guide to Immune-Mediated Hemolytic Anemia (IMHA) in Dogs and Cats (2025) 🐶🐱

By Dr Duncan Houston BVSc

Immune-Mediated Hemolytic Anemia (IMHA) is a dangerous autoimmune disease in which the body destroys its own red blood cells 🧬. This leads to severe anemia, jaundice, blood clots, and life-threatening complications. Early diagnosis and aggressive treatment are critical. In this 2025 guide, Dr Duncan Houston explains IMHA, including symptoms, testing, treatment, and prognosis 🩺.

⚠️ What Is IMHA?

In IMHA, the immune system marks red blood cells for destruction, even though they are healthy. This leads to:

• 📉 Severe anemia (low red blood cell count)
• 🟡 Jaundice (yellow skin, eyes, and urine)
• 💥 Formation of blood clots (thromboembolic disease)

Mortality ranges from 20–80% depending on how quickly treatment is started and how severe the case is.

🧬 Normal vs. IMHA Red Blood Cell Breakdown

In healthy pets:

• 🧪 Red blood cells live ~120 days, then are recycled by the spleen, liver, and bone marrow
• 🌟 Hemoglobin is converted to bilirubin and excreted safely

In IMHA:

• 🧫 Antibodies coat red blood cells and mark them for destruction too early
• 🔥 The spleen and liver overwork, bilirubin builds up, and clots begin to form

🔍 Symptoms of IMHA

• 😴 Lethargy and weakness
• 💧 Pale or yellow gums
• 🍊 Orange or brown urine
• 📉 Loss of appetite and fever
• 🔴 Dark gums or mucous membranes (in advanced cases)

IMHA often comes on quickly—any combination of these symptoms should prompt immediate vet care ⚠️.

🧪 Diagnosing IMHA

Key Tests:

• 🧬 Blood smear: identifies spherocytes (damaged red cells) and autoagglutination (cells clumping)
• 🧪 Coombs test: confirms red blood cells are being attacked by antibodies
• ⏱️ PT/PTT tests: measure clotting function
• 📊 Lactate levels: high levels = poor oxygenation = worse prognosis
• 🦠 Parasite testing: rule out tick-borne diseases (Babesia, Ehrlichia, Anaplasma)

💉 Treatment and Monitoring

1. Blood Transfusions

• 🩸 Restores oxygen-carrying capacity
• ⚠️ May need multiple transfusions

2. Immune Suppression

• 💊 Prednisone or dexamethasone – cornerstone of treatment
• 🧬 Additional meds (azathioprine, cyclosporine, mycophenolate) if response is poor or to taper steroids

3. Preventing Blood Clots

• 💉 Heparin or clopidogrel to prevent thromboembolic disease (main cause of death)
• 🥄 Low-dose aspirin may help but must be used cautiously

4. Monitoring

• 📆 Frequent blood tests to track red blood cell count, liver enzymes, and clotting function
• 🧪 Urine checks to monitor kidney involvement

🧪 Complications and Special Situations

Evans Syndrome

When red blood cells and platelets are being destroyed simultaneously. Prognosis is worse due to higher bleeding risk and difficulty managing both problems ⚠️.

Thromboembolic Disease

• 🧱 Blood clots (embolisms) block organs
• ⚠️ Responsible for 30–80% of IMHA deaths

Gamma Globulin Therapy

💉 A rescue therapy in critical cases—rare and expensive but may help dogs unresponsive to conventional treatment.

📊 Prognosis and Relapse Risk

Mortality: 20–80% depending on speed of diagnosis, severity, and response to treatment.

• 📆 Most relapses occur within 2–3 months
• 🔄 Lifelong low-dose immunosuppression may be needed

📈 Breed Risk Factors

• 🐶 Cocker Spaniels
• 🐩 Poodles
• 🐕 Old English Sheepdogs
• 🧡 Irish Setters

In cats, IMHA is most commonly associated with Mycoplasma hemofelis or feline leukemia virus (FeLV).

💉 IMHA & Vaccination

Though unproven, there’s debate about whether vaccination can trigger IMHA in some dogs. Many clinics have moved to a 3-year DHPP schedule 🛡️. Discuss your dog’s risk factors with your veterinarian before future vaccines.

📲 Final Advice from Dr Duncan Houston

IMHA is a life-threatening disease, but survival is possible with early recognition and aggressive care 💪. If your pet shows signs of lethargy, jaundice, or dark urine—don’t wait.

📱 For help monitoring IMHA, managing medications, or spotting relapse, download the Ask A Vet App or visit AskAVet.com. Early treatment saves lives 🩺🐾.