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

By Dr. Duncan Houston, BVSc

Immune-mediated hemolytic anemia (IMHA) is a critical autoimmune disease where a pet’s immune system mistakenly attacks and destroys its own red blood cells 🛑. This leads to severe anemia, tissue damage, and life-threatening complications. Prompt diagnosis and aggressive treatment are essential to improve survival outcomes 🐾🩺

🔬 What Is IMHA?

IMHA (formerly AIHA) occurs when antibodies coat red blood cells, flagging them for destruction. This leads to:

• 🩸 Severe anemia (loss of red blood cells)
• 🟡 Jaundice (yellow tissues, gums, or eyes)
• 🔁 Life-threatening blood clots (thromboembolism)
• 🧪 Hemoglobin in blood/urine, overwhelming kidneys

⚠️ Signs to Watch For

• 😴 Weakness or lethargy
• 🍽️ Loss of appetite
• 🟠 Orange/brown urine
• 👅 Pale or yellow gums
• 🌡️ Fever or collapse

If your pet shows these signs, see a veterinarian IMMEDIATELY. Time is critical ⏱️

🧪 Diagnostic Features

Diagnosis is based on clinical signs + specific blood findings:

• 🧬 Presence of spherocytes on blood smear (partially destroyed red cells)
• 🔬 Autoagglutination—blood clumping visibly on a slide
• 🧪 Coombs test—confirms red cells are antibody-coated
• 🧪 Lactate levels—high values suggest poor oxygenation and predict survival
• 🦠 Tick-borne disease tests to rule out blood parasites like Babesia or Ehrlichia

🩺 Emergency Treatment

1️⃣ Blood Transfusions

Needed when red blood cell levels drop dangerously low. Even though the immune system may attack transfused cells, transfusions are life-saving 🔄🩸

2️⃣ Immune Suppression

• 💊 Prednisone or dexamethasone—first-line drugs to suppress antibody production
• 💊 Azathioprine, cyclosporine, or mycophenolate—used if response is poor or to reduce steroid side effects

Expect months of therapy. Corticosteroid side effects are common but taper as dosing is reduced 📉

3️⃣ Clot Prevention

• 💉 Heparin or low-dose aspirin—to reduce clot formation
• 💊 Clopidogrel—an alternative anti-clotting agent

🧠 Clots (thromboembolic disease) are the leading cause of IMHA-related death. Prevention is critical 🚫🩸

📊 Prognosis

Mortality rate is 20–80%, depending on early detection, severity, and treatment strategy. Factors affecting outcome:

• 🐾 Presence of thromboembolism
• 📈 Extremely high white blood cell counts (leukemoid response)
• 🧪 Persistently high lactate levels (poor oxygenation)
• 🧬 Underlying triggers (e.g., parasites, cancer, medications)

📚 Study Highlights

Large studies (e.g., Cornell, University of Wisconsin) showed:

• 🐶 Cocker spaniels and schnauzers are overrepresented
• ♀️ Unspayed females and neutered males at higher risk
• 🧪 Most cases showed spherocytes and autoagglutination
• 🧪 70% needed at least one transfusion
• ⚰️ 100% of fatal cases had thromboembolism on necropsy

🔄 Relapse Risk

• ♻️ Relapse occurs in 11–15% of IMHA survivors
• 🧪 Ongoing monitoring and tapering of medications is essential

👩‍⚕️ Evans Syndrome

This is when IMHA is combined with immune-mediated thrombocytopenia (destruction of platelets). It is especially dangerous as patients may have no ability to form blood clots at all.

🧬 What Causes IMHA?

• 🦠 Unknown in 60–75% of dog cases
• 💉 Sometimes triggered by medications, vaccines, or infections
• 🎯 In cats, often linked to FeLV or Mycoplasma hemofelis

📈 Long-Term Monitoring

• 🧪 Regular blood tests (hematocrit, bilirubin, Coombs, lactate)
• 📅 Monitor steroid side effects
• 🩺 Watch for return of weakness, pale gums, or jaundice

📲 Get Help for Your Pet

IMHA is serious, but survival is possible with prompt treatment and vigilant care. For expert support or treatment planning, visit AskAVet.com or download the Ask A Vet app 📱

🩸 Let’s give your pet the strongest chance to overcome IMHA—together 💪🐾