Myelodysplastic Syndromes in Dogs

Myelodysplastic syndromes are a group of disorders affecting the dog's hematopoietic stem cells, which forms all the types of blood cells in the body (i.e., red blood cells, white blood cells, platelets). These disorders are characterized by the abnormal development and maturation of hematopoietic stem cells, and may be primary (congenital) or secondary (due to cancer, drugs exposure, and/or infections).

Myelodysplastic syndromes more common in cats than dogs.

Symptoms and Types

• Weakness
• Lethargy
• Pale mucous membranes
• Weight loss
• Excessive bleeding
• Recurrent infections
• Enlargement of spleen and liver

Causes

• Infections
• Bone marrow dysplasia
• Immune-mediated neutropenia (due to steroids)
• Drug toxicity (e.g., estrogen, cytotoxic anticancer agents, or trimethoprim and sulfa combination)

Diagnosis

You will need to give a thorough history of your dog’s health, including the onset and nature of the symptoms, to your veterinarian. He or she will then conduct a complete physical examination, as well as a biochemistry profile, urinalysis, and complete blood count (CBC). Blood testing is especially important in making the diagnosis, as it may reveal abnormal reduction in the number of blood cells (cytopenia). In some dogs, megaloblastic anemia is also seen.

Other abnormal findings may include large, bizarre platelets and immature granulocytes (type of white blood cells) with abnormal shape and sizes. Your veterinarian will also take bone marrow sample to evaluate the red blood cell and white blood cells production process and identify abnormalities.