Stem Cell Disorders Due to Abnormal Development and Maturation in Dogs

Your dog’s body is constantly creating new blood cells, but in myelodysplasia syndrome those cells are abnormal or they are not able to grow to maturity. Without these mature blood cells, your dog will eventually get thrombocytopenia, enlarged erythrocytes, anemia, neutropenia, and leukopenia. There are two types of myelodysplasia syndrome, which are primary and secondary. The primary type of myelodysplasia syndrome is thought to be caused by stem cells that have spontaneously mutated in your dog’s body. Secondary myelodysplasia syndrome is most likely caused by an outside source, such as some forms of medications like radiation treatments.

Stem cell disorders due to abnormal development (Myelodysplasia Syndrome) is a disorder that is described as ineffective myeloid blood cell regeneration. This means that the blood cells are being created, but fail to grow to maturity. It can happen in any or all of the blood cells (red, white, platelets) and causes low cell counts. There are primary and secondary versions of this syndrome: primary syndrome is commonly caused by mutated stem cells that form a tumor and secondary syndromes are caused by or some form of drug therapies. Without treatment, myelodysplasia syndrome will often progress to leukemia.

The symptoms of myelodysplasia syndrome depend on the cause and the type that your dog has.

Primary Myelodysplasia Syndrome

• Lethargy
• Appetite loss
• Losing weight
• Anorexia (refusal to eat at all)
• Pale mucous membranes and skin
• Dark red or purple dot on skin
• Chronic high body temperature
• Extreme thirst
• Abdominal pain
• Vomiting
• Diarrhea (runny stool)

Secondary Myelodysplasia Syndrome

• Exhaustion
• Increased water consumption
• Loss of appetite
• Shortness of breath
• Lameness in one or all legs (inability to walk)
• Muscle loss
• Bruising
• Red rash
• Vomiting
• Diarrhea (runny stool)
• Confusion
• Fainting
• Seizures

 Types

Primary myelodysplasia syndrome occurs when the stem cells in your dog’s body mutate and form a cancerous tumor.

 Secondary myelodysplasia syndrome can occur when your dog is treated with some form of treatment that alters the stem cells, such as with radiation treatments for cancer.

Primary Myelodysplasia Syndrome

• Spontaneous mutation in stem cells
• Cancerous tumor growth
• Infectious diseases
• Severe nutritional deficiency

 Secondary Myelodysplasia Syndrome

• Radiation therapy
• Chemotherapy
• Benzene
• Cigarette smoke

The veterinarian will need to know about your dog’s medical history if he does not already have it. Additionally, your veterinarian will ask how long the symptoms have been going on, if they have worsened, if there are any differences in behavior, changes in food or shampoos, activity level, etc. Once the veterinarian gets all of the information he needs from you, he will do a thorough examination of your dog, including blood pressure, body temperature, and abdominal palpation. Some tests will need to be done to rule out other disorders that mimic myelodysplasia syndrome, such as canine ehrlichiosis, renal diseases, polycythemia vera, acute leukemia, macrocytosis, and some cardiac diseases. These tests are:

• Blood chemical panel (phosphorus, potassium, sodium, protein, creatinine, calcium)
• Complete blood count (CBC)
• Blood urea nitrogen (BUN)
• Glucose test (blood sugar level)
• Urinalysis (color, concentration, clarity)
• Bone marrow aspiration
• Biopsy (bone marrow)
• Digital radiographs (x-rays) of the chest and abdomen

 The veterinarian may also want to confirm that your dog has myelodysplasia syndrome

• Spinal tap (cancerous neoplastic cells)
• Ultrasound of the kidneys
• Biopsy (lymph nodes, liver, spleen)

Your dog’s veterinarian will probably hospitalize your dog to treat him with fluid therapy and medications. The medicine, Epoetin (recombinant human erythropoietin), is often used for treatment of primary myelodysplasia syndrome with positive results, although some are resistant to this drug. Prednisone is also used for myelodysplasia syndrome to help reduce inflammation and pain. Blood transfusions can be helpful in slowing the disease, and in some cases has been known to actually reverse and stop it completely. If the primary myelodysplasia syndrome is caused by a cancerous tumor, radiation may be an option, but it is risky since it also can cause your dog’s stem cells to mutate.

Secondary myelodysplasia syndrome is treated by stopping the drug therapy that your dog has been on unless it is needed for survival. If that is the case, the veterinarian will use supportive treatments such as blood transfusions and medications. Similar to primary myelodysplasia syndrome, the medications used will be epoetin and prednisone. These drugs can also cause changes to the stem cell development in some dogs, so the veterinarian will weigh the risks against the benefits before suggesting this route.

Unfortunately, both primary and secondary myelodysplasia syndrome will usually progress to leukemia in less than a year, although there is some success with epoetin and prednisone treatment. Secondary myelodysplasia syndrome can be reversed if the veterinarian thinks it is safe to stop the medication or other toxin that is causing it, and give your dog a blood transfusion.

If your dog does progress to leukemia, the prognosis is poor. The average dog with leukemia either dies of anemia, sepsis, or a bleeding complication within a few months. Many owners choose to euthanize to stop their dog from suffering.