Bone marrow is the spongy tissue at the core of the long bones in a pet’s skeleton. The primary function of the bone marrow is to produce new blood cells, including red blood cells, white blood cells and platelets. These cells provide life sustaining oxygen, help our pets fight off infection and aid in blood clotting.
Bone marrow suppression causes a disruption in the production of one or more of these blood lines, and when this occurs, severe consequences can result. Each blood line serves a very important purpose in a pet’s body. Let’s investigate what a lack of each would look like:
Red blood cells
When red blood cell levels are low, we call it anemia. We’ve talked extensively about anemia before, both due to blood loss and destruction by the body’s own immune system. When pets are anemic, they don’t have enough red blood cells to carry sufficient oxygen to the tissues of our body. Clinical signs of anemia include lethargy and pale gums.
White blood cells
Low white blood cell numbers is called leukopenia. Leukocytes (or white blood cells) fight infection in a pet’s body. Inadequate numbers weaken our pet’s immune system dramatically, rendering them unable to fight off bacterial, viral and fungal infections.
A low platelet level is also known as thrombocytopenia. Because platelets are responsible for sealing up tiny holes that occur continuously in our pet’s blood vessels, when their numbers fall, holes go unpatched and blood vessels become leaky. Clinical signs of thrombocytopenia include prolonged bleeding from wounds and bruising.
Bone marrow suppression can affect just one line, resulting in just anemia or just thrombocytopenia, for example. Or it can affect all three blood lines, which is a condition we call pancytopenia.
There are many different reasons that a pet can undergo bone marrow suppression, but one of the most common reasons for it is the use of chemotherapeutic drugs. Bone marrow cells divide rapidly, making them a target for chemotherapy drugs that also target rapidly dividing cancer cells. Bone marrow cells often fall in the line of fire during cancer treatments that involve chemotherapy for this reason.
Other causes of bone marrow suppression include:
- drugs prescribed to treat illness
- chronic disease, such as kidney or liver disease
- nutritional imbalances
- estrogen exposure
- infections, like canine ehrlichiosis
Your veterinarian will be able to diagnose low red cell, white cell and platelet levels with a routine blood test called a CBC (complete blood count), but determining the underlying cause for the bone marrow suppression will be a more difficult task requiring additional diagnostics.
Treating bone marrow suppression will center on addressing its cause. If chemotherapy is the cause of bone marrow suppression, treatments may be delayed if blood cell numbers fall too low. Supportive treatments, including blood or platelet transfusions and antibiotics may be needed while the search for the underlying cause is conducted.