IMHA in Cats: Diagnosis and Treatment

What Is IMHA in Cats?

IMHA stands for immune-mediated hemolytic anemia. The best way to understand what IMHA means is break it apart into each individual word. 

• Immune-mediated: The condition is caused by the immune system attacking its own cells. 
• Hemolytic: Hemolysis is the destruction of red blood cells. With IMHA, the red blood cells are getting destroyed by the body’s own immune system. 
• Anemia: Anemia means there are too few red blood cells in circulation. A cat with IMHA gets anemia because the red blood cells are being destroyed. 

You may also see IMHA referred to as AIHA, which stands for autoimmune hemolytic anemia. This is the same condition. 

IMHA is an emergency. If you suspect your cat may have IMHA, call the emergency veterinarian. 

Symptoms of IMHA in Cats

The following are symptoms of IMHA in cats: 

• Breathing quickly (tachypnea) or difficulty breathing (dyspnea) 
• Lethargy, weakness, or collapse 
• Discolored urine (dark brown) 
• Pale or yellow-tinged gums or ears (jaundice)  
• Fast heart rate (tachycardia) 
• Poor appetite 
• Vomiting or diarrhea 

Causes of IMHA in Cats

IMHA in cats can be primary or secondary. With primary IMHA, there is no known cause. This is also called idiopathic IMHA. 

Secondary IMHA happens when there is an underlying trigger that causes the immune system to attack its own red blood cells. While primary IMHA is more common in dogs, secondary IMHA is more common in cats.  

Secondary IMHA is usually triggered by infections, cancer, or toxins. Common triggers in cats include:  

• Mycoplasma haemofelis 
• Feline leukemia (FeLV) 
• Feline immunodeficiency virus (FIV) 
• Feline infectious peritonitis (FIP) 
• Lymphoma 

IMHA is more common in cats under three years old. Males may be overrepresented, which might be because of an increased likelihood of certain conditions like FIV. 

How Veterinarians Diagnose IMHA in Cats

Your veterinarian may recommend the following tests to diagnose IMHA in cats: 

• Routine blood work and urinalysis: Blood work will usually show low red blood cell counts and increased white blood cell counts. Platelets may also be low. Urine will be a brownish color but won’t usually have blood in it. 
• Microscopic examination of blood: The veterinarian may see changes to the size and look of red blood cells. They may also see visible red blood cell parasites that are triggering IMHA. 
• FIV/FeLV testing: This is a blood test that can diagnose two potential causes of secondary IMHA. 
• Imaging: X-rays and ultrasounds of the chest and abdomen may be done to search for tumors that could trigger IMHA. 
• Additional blood tests: Other blood tests may be recommended to diagnose conditions like M. haemofelis if the parasites aren’t visually identified on red blood cells. A Coombs test looks for autoimmune destruction of red blood cells. 

Make sure to let the veterinarian know: 

• Whether your cat has outdoor access 
• The cat’s vaccination and parasite prevention history 
• Any known toxin or medication exposures 

Treatment of IMHA in Cats

Treatment of IMHA in cats centers on suppressing (holding back) the immune system, providing supportive care, and managing any underlying causes. 

Cats with IMHA will usually need to be hospitalized for around-the-clock care. An intravenous (IV) catheter is usually placed to give fluids, blood transfusions, and IV medications. 

Most cats with IMHA will need at least one blood transfusion. The veterinarian will make sure that your cat’s blood type is compatible with the donor cat’s blood type before transfusion. 

Immunosuppressive medications are given to stop the immune system from attacking its own cells. Prednisolone is a common steroid used to suppress the autoimmune attack of red blood cells.  

If steroids alone aren’t enough, other immunosuppressive medications like cyclosporine may be added.  

Treatment with immunosuppressive medications generally lasts at least three to six months and then is slowly tapered down. 

Underlying causes need to be managed if possible. For example, cats with mycoplasmosis are treated with doxycycline for two to four weeks.  

Some underlying causes of secondary IMHA, such as FeLV, are unlikely to get better. Humane euthanasia may be recommended for these pets to prevent suffering. 

Recovery and Management of IMHA in Cats

Expect that your cat with IMHA will be hospitalized for a couple days, potentially up to a week.  

For the first few weeks after hospitalization, frequent rechecks will be recommended to ensure that the immunosuppressive medications are working. Steroids and other immunosuppressive medications are usually continued for several months and then slowly reduced. 

Relapse is possible, though the reported relapse rate for IMHA in cats varies significantly between studies. 

Prevention of IMHA in Cats

Not all cases of IMHA in cats are preventable, as primary IMHA usually occurs with no known cause. Some causes of secondary IMHA, such as cancer, are also not necessarily preventable.

However, some causes of secondary IMHA can be prevented. The following tips may lower the risk of secondary IMHA in cats: 

1. Keep your cat indoors to reduce the risk of infectious disease transmission. 
2. Keep your cat on flea and tick prevention to prevent certain blood parasites. 

3. Vaccinate your cat against feline leukemia. 

4. Keep toxins and drugs locked safely away so your cat cannot eat them.