About IMHA

 

Immune-Mediated Hemolytic Anemia (IMHA) or Autoimmune Hemolytic Anemia (AIHA) is a devastating condition that requires emergency care and possibly hospitalization. Mortality rates are difficult to determine but are estimated at 28%-70%. This blog post is meant to not only bring awareness to IMHA, but also to remind you to prepare for such a crisis with pet health insurance or a savings account specifically designated for your companion animals.

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Definitions

Anemia – A condition in which a body does not have enough healthy red blood cells. It can have many causes such as iron deficiency, excessive blood loss, malnutrition, parasitism, and an immune-mediated attack. 
Immune-Mediated/Autoimmune – The body’s immune system attacks and destroys healthy body tissue by mistake.
Hemolytic – Refers to hemolysis, the destruction of red blood cells which leads to the release of its hemoglobin into the blood plasma.

 

Putting it altogether. Immune-Mediated Hemolytic Anemia is “low blood count” due to the destruction of red blood cells caused by the body’s immune system attacking them.

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Symptoms

Unfortunately, no single symptom can tell you that your pet is suffering from IMHA. Rather, the animal could suddenly look very pale or jaundiced (gums) and could be weak and collapse.

 

IMHA symptoms can include and range from weakness, lethargy, poor appetite, fainting, exercise intolerance, vomiting, rapid breathing, diarrhea, thirst, fever, jaundice, rapid heart rate, melena (black feces due to bleeding into the bowel.  The body often destroys blood platelets as well, resulting in Immune–mediated or idiopathic thrombocytopenia, IMTP or ITP (a thrombocyte is another name for a platelet). In these cases, there are petechia (red, purple pinpoint hemorrhages in the skin), and ecchymoses (bruises in patches of the skin).

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Causes

IMHA is further classified into “primary” and “secondary”. Primary IMHA is essentially idiopathic – the body just starts attacking itself for no known or obvious reason.  With secondary IMHA, an assortment of various environmental and physiological factors can trigger it such as bee stings or other insect bites, heartworm disease, stress events, sex hormonal cycle changes, toxins, certain drugs and chemicals, and infectious diseases  like  and leptospirosis. Ironically, things meant to protect and repair the body –  maternal/fetal antibody incompatibility at birth (neonatal isoerythrolysis), certain antibiotics and vaccines – can actually be an underlying cause. But, IMHA and IMTP occur in genetically predisposed individuals, which is why even fully recovered animals should not be used for breeding, and caution should apply to breeding the parents and other close relatives.  

 

Diagnosis

Your veterinarian will need to perform a thorough physical examination, and run a comprehensive blood panel, including the direct Coombs test for antibodies coating the surface of the red blood cells, and anurinalysis.  In the acute phase of IMHA, the blood may appear autoagglutinated (clumped red cells) in the syringe or test tube, confirming the likely diagnosis of this emergency situation.

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