Why Is My Dog Or Cat's Blood Lymphocyte Count High Or Low ?













Ron Hines DVM PhD

To see what normal blood and urine values are, go here

For an explanation of causes of most abnormal blood and urine tests, go here

To see how tests are grouped, go here

Changes In Your Pet's Lymphocyte Count = Lymphs, Lymphos

I find Lymphocytes the most interesting cells in your pet’s circulation. That is because of their complex origins and the intricate things they constantly do to keep your pet healthy. When results come back from your pet’s CBC/WBC count and blood chemistry panel, the number of lymphocytes in the dog or cat 's blood will be given as a total number per volume of blood (the absolute count) as well as the percentage of the total white blood cell count that lymphocytes comprise. Although there are three major types of lymphocytes (all with very different functions) , the automated blood analyzers of today generally lump them together. If a sizable portion of them are “atypical” in shape or the count is unusual in number, the machines can “flag” them for verification by hand using older, microscopic methods (then you should se “verified by smear” written as a side note). In those cases, the stained characteristic of individual lymphocytes are added as a note to the bottom of your pet’s lab report.


Reasons Why Your Pet’s Lymphocyte Numbers (Count) Might Be High (Lymphocytosis) :

Excitement fear and sudden stress are probably the most common causes of minor increases in the lymphocyte count.

Discontinuing long-term corticosteroid medications can cause a temporary increase in lymphocyte numbers.

Lymphocyte counts are often a bit higher higher in puppies, kittens and younger pets.

Cholangiohepatitis, fever of unknown origin, IBD, autoimmune disease, blood parasites (hemobartonella, ehrlichia) , hyperthyroidism, Addison's disease and some medications (eg methimazole) can all raise lymphocyte counts.

In older dogs and cats, , lymphocytic leukemia, lymphoma, pure red cell aplasia in cats (probably an autoimmune disease of the bone marrow) , immune-mediated hemolytic anemia, thymoma tumors,

Lymphoma/lymphosarcoma or lymphocytic leukemia cancers can make total lymphocytes counts go both up or down.

The most common reason for falsely-high lymphocyte counts in automated counting is mistaking abnormal, nucleated red blood cells for lymphocytes. Cancerous myeloma cells can also confuse the machines.

What If It Is Noted That Some Lymphocytes Are “Atypical” or “Reactive” ?

The presence of these larger-than-normal lymphocytes in increased number (often with unusual stain colorations) indicates that your pet’s immune system is responding to something. It doesn’t tell your veterinarian what that "something" is. It could be an infection (such as Ehrlichia in dogs), it could be a recent vaccination or even a tumor.

When unusual numbers of atypical lymphocytes are seen, request that a clinical pathologist at the lab review them and the rest of the tests that were run. Sometimes, pursuing the cause with a lymph node biopsy might be warranted. That's for the laboratory pathologist to decide.

Reasons Why Your Pet’s Lymphocyte Numbers Might Be Low (Lymphopenia) :

Low lymphocyte numbers occur most commonly after pets receive corticosteroid medications or when their adrenal glands produce too much cortisol (Cushing’s disease).

Less reliably low numbers (lymphopenia) occurs early in parvovirus and distemper infection in dogs and in panleukopenia of cats or after prolonged periods of stress.

Low lymphocyte counts, sometimes accompanied by fever, are also a common finding in cats with FIP. (ref)

Your pet's blood lymphocyte numbers can also go down when lymphocytes are lost into retained fluids (chylothorax) and in immune system malfunctions. Dogs and cats with significant kidney disease often have lower than normal blood lymphocyte numbers as well - probably due to a build up of toxic waste products in their bloodstream. (ref)

Some of my clients have been concerned that their elderly pet's lymphocyte counts report back from the lab as somewhat low. I do not know of any studies in cats or dogs, but lower lymphocyte counts are a normal result of the aging process in us humans. (ref)

Complementary Tests :

They would be based on the rest of your pets WBC count and blood chemistry values, suggestions from the testing lab's clinical pathologist and your veterinarians experience in dealing with the symptoms your pet is experiencing.