Your dog's red and white blood cells, along with his platelets, originate in his bone marrow. Anemia results when the bone marrow doesn't produce sufficient numbers of red blood cells, which carry oxygen to the body's cells. Severe anemia in dogs can cause myelofibrosis, a condition whereby bone marrow tissue starts dying. Fortunately, canine myelofibrosis is relatively rare.
Canine myelofibrosis falls into the category of myeloproliferative diseases, all of which concern issues in the bone marrow. Myelofibrosis occurs when the bone marrow begins turning into fibrous connective tissue. The District of Columbia Academy of Veterinary Medicine describes myelofibrosis as an "end stage" marrow, similar to cirrhosis of the liver. Any dog might develop the disorder -- there is no particular breed or gender susceptibility. One primary disease causing myelofibrosis, pyruvate kinase deficiency, occurs most often in basenjis, beagles, cairn and West Highland white terriers.
Canine myleofibrosis usually occurs as a secondary condition of other diseases, or results from treatments for other maladies. Diseases and disorders include congenital hemolytic anemia, myeloid metaplasia, ehrlichiosis -- a disease contracted from ticks -- and septicemia, or blood poisoning. Radiation can cause myleofibrosis, as can the reaction to certain drugs. These medications, taken long-term, include phenobarbital and dilantin, often given to dogs experiencing seizures; the anti-inflammatory phenylbutazone, and colchicine, used for certain liver ailments.
If your dog is undergoing treatment for certain diseases, your vet carefully monitors your pet. Dogs suffering from myelofibrosis display signs of anemia, including lethargy, weakness, rapid heartbeat and pale mucous membranes. If the myleofibrosis is drug-related, your dog might be fine on the particular medication for quite some time, until the anemia develops. Diagnosis is made via aspiration of the bone marrow or bone marrow biopsy, both of which require anesthesia.
To treat myelofibrosis, your vet might prescribe steroids, along with hormones such as erythropoietin. If the condition resulted because of long-term drug treatment for another illness, your vet might have to prescribe other medications to combat the primary disease. The prognosis depends on whether the bone marrow tissue becomes necrotic, or dies. It also depends on the primary disease affecting your dog and the ability to treat it if your pet can no longer tolerate effective medications.
By Jane Meggitt
National Canine Cancer Foundation: Myeloproliferative Diseases
District of Columbia Academy of Veterinary Medicine: Current Chemotherapy in Oncology
University of Prince Edward Island: What Is Pyruvate Kinase (PK) Deficiency?
National Center for Biotechnology Information: A Retrospective Study of 19 Cases of Canine Myelofibrosis
SAGE Journals: Histopathology of Bone Marrow
About the Author
Jane Meggitt has been a writer for more than 20 years. In addition to reporting for a major newspaper chain, she has been published in "Horse News," "Suburban Classic," "Hoof Beats," "Equine Journal" and other publications. She has a Bachelor of Arts in English from New York University and an Associate of Arts from the American Academy of Dramatics Arts, New York City.