Q Our 6-year-old cocker spaniel is in the hospital with what our veterinarian is saying is a serious illness. We noticed several days ago she did not want to go on her walks and was not eating as much. Then yesterday she collapsed, so we rushed her to the hospital. Our veterinarian says she has hemolytic anemia. She looks very ill to us but we do not know how worried we should be.

A: There are many causes for anemia, which means a low red blood cell count. We break anemia into three groups of causes to help us figure out the cause and then the treatment options.

Bleeding is usually obvious and indicates blood loss from the body faster than it can be replaced. The second cause of anemia is where the bone marrow, which makes new red blood cells, is diseased and cannot keep up with demand. The third group of diseases is called hemolysis. This is where red blood cells are being destroyed in the body.

There are multiple causes for hemolysis. Different infections and cancers can be associated with this disease. The most common cause, however, is where the immune system attacks itself and we call this immune mediated hemolytic anemia, IMHA.

What happens is the body produces antibodies that attach to the red blood cells. These antibodies coat the red blood cells, essentially marking them to be removed from the blood stream as if they are an invading infection. When the rate of removal is greater than the ability of the bone marrow to make new cells, the dog becomes anemic.

The first symptom you notice at home is often the one you noted, weakness. Anemia usually causes the gums to become pale.

Jaundice is the next symptom noted. This occurs when the rapid destruction of blood cells exceeds the body's ability to remove the broken components of the cells from the body. Bilirubin is a yellow pigment that is produced when blood cells are broken down. Under normal conditions, the liver removes it from the blood and puts it into the gall bladder where it is eliminated from the body. When there is excessive hemolysis, however, the liver is overwhelmed and bilirubin levels increase, causing the gums, eyes and urine to become yellow.

Any cause of sudden anemia is an emergency, so when noted, it is important to seek veterinary help as soon as possible. With immune mediated hemolytic anemia, the sooner therapy is started, the better.

Treatment has two components: stopping the immune system from attacking the red blood cells and keeping the patient alive until the immune attack can be stopped.

High doses of corticosteroid hormones are the cornerstone of treatment because they act rapidly by decreasing the antibodies that are coating the red blood cells. They also slow the removal of antibody-coated red blood cells. Prednisone and dexamethasone are the most commonly used corticosteroids.

Unfortunately, corticosteroids have side-effects, the most common being excessive thirst, increased urination, redistribution of body fat, thin skin, panting and increased risk of urinary-tract infections. Because they are the best first-line treatment, these side-effects have to be tolerated initially to save the dog's life. In most patients, the corticosteroids can be gradually decreased or even stopped. This process is done slowly over several months to prevent a relapse.

Most of the time, another immunosuppressive agent will be started along with the corticosteroid. The goal of these medications is to compliment the corticosteroid as well as hopefully allow it to be stopped sooner. Azathioprine and cyclosporine are the two most commonly used. These medications do not work as quickly as the corticosteroids, so they are never the first therapy.

Blood transfusions are the primary treatment given to keep the patient stable until the medications kick in. It is variable how many, if any, transfusions a dog will require. It is not uncommon for three to four to be needed over the initial week of therapy.

Besides the life-threatening anemia, the disease also predisposes the dogs to blood clot formation, called thromboembolic disease. If these clots are large enough and obstruct blood in a critical location, such as the lungs, they can be fatal. Low-dose aspirin may help decrease the chances of this complication.

Most of the time, we do not know why the immune system decides to attack its own red blood cells. Certain breeds appear to be predisposed, including cocker spaniels, poodles, old English sheepdogs and Irish setters.

Depending on the study, anywhere from 25 percent to 60 percent of dogs diagnosed with this condition will die. When a patient responds, it also is not quickly fixed and requires owners committed to long-term follow-up and patience with medication side-effects.

Dr. Henri Bianucci and Dr. Perry Jameson are with Veterinary Specialty Care LLC. Send questions to petdocs@postandcourier.com.