There are different diseases in dogs that can affect the organs and tissues of their body. Some of these are medullary, which means that they affect the internal regions of internal organs and tissues. Medullary aplasia is one of those diseases that affects the bone marrow of dogs. This disease is related to the ability of the marrow to produce blood cells.
In this post, we discuss the symptoms and treatment of bone marrow aplasia in dogs. We will also look at the causes and possible treatment options available.

What is medullary aplasia?

The hypoplasia of the erythroid, myeloid and megakaryocytic lines, precursors of blood cells that originate in the bone marrow, is called medullary aplasia or bone marrow aplasia. Because of this, there is a reduction in red blood cells or erythrocytes, white blood cells or leukocytes, or platelets in the peripheral blood. Medullary aplasia is complete if all the precursors are affected or partial if only some are affected. In addition, the absence of hematopoietic tissue is replaced by adipose tissue, occupying up to 95%.

The main causes of bone marrow aplasia in dogs

Bone marrow aplasia in dogs can occur from the following causes:

  • Drugs: exposure to chemotherapy, azathioprine, trimethoprim / sulfadiazine, exogenous or endogenous estrogens, phenylbutazone, cephalosporins, phenothiazine, captopril, or chloramphenicol.
  • Environmental toxins: insecticide, benzol, varnish or paint.
  • Microorganisms: Ehrlichia canis (Ehrlichiosis) that infects the progenitor and proliferative cells of the bone marrow.
  • Hematopoietic neoplasia: abnormal growths in the hematopoietic cells of the bone marrow.
    Chronic kidney failure: has various causes and symptoms.

Additionally, a congenital red blood cell aplasia called Diamond-Blackfan anemia has been described in dogs, specifically affecting young dogs. This causes absence of erythroid precursors, but the others are intact. An idiopathic or primary aplasia, apparently of immune-mediated origin, is also known, since it responds to corticosteroid therapy.

Symptoms of Medullary or Bone Marrow Aplasia in Dogs

The clinical picture of canine aplastic anemia will vary according to the degree of bone marrow cell involvement. Total pancytopenia is the most serious, since it will cause symptoms related to the lack of red, white and platelet cells: there are several consequences in the affected dog and it is lethal in some cases.

Symptoms associated with red cell aplastic anemia (the one caused by a lack of red blood cells) are similar to other forms of anemia. They include:

  • Pale mucous membranes.
  • Tachycardia (fast heart rate).
  • Tachypnea (rapid breathing).
  • Fatigue.
  • Weakening.
  • Exercise intolerance
  • Palpitations

When white blood cells are missing, the lack of immune cells responsible for the dog’s immune response causes the dog to have a lower immunity. This makes the dog susceptible to all kinds of infections. This is why this disease can cause osteomyelitis in dogs if the bone itself is infected.

If platelets are missing, dogs will have a tendency to bleed profusely, as platelets are involved in blood clotting. These bleeds can be minor, such as oral or nasal bleeding. In the worst case, they will occur in internal organs, such as the digestive system or the brain, putting the dog’s life at risk.

Diagnosis of bone marrow aplasia in dogs

The diagnosis of medullary aplasia is made with a blood test. This canine blood test will be used to evaluate the number of red, white and platelet blood cells, which are decreased in this disease. Acute canine leukemias should be included in the differential diagnosis.

Once the reduction in bone marrow capacity is confirmed, a bone marrow sample should be taken by aspiration or biopsy:

  • Aspiration samples allow individual cell shape to be assessed and the myeloid-erythroid ratio determined.
  • The biopsy indicates the structure of the marrow and its global cellularity. It is the technique of choice in cases of hypocellular marrow or that has been replaced by fatty tissue. In this sample the absence of hematopoietic cells will be observed.

Bone marrow samples

Dog bone marrow samples are taken at the following sites:

  • Proximal epiphyses of the humerus and femur.
  • Iliac crest.
  • Wing of the ilium.
  • Ribs.
  • Breastbone.

Both aspiration and biopsies can be very uncomfortable for the dog. They are often done under general anesthesia.

Treatment of medullary aplasia in dogs

Treatment of medullary aplasia in dogs will depend on the type of cells affected. In general, we can see the following treatment options:

  • Antibiotics and asepsis: in cases of leukocyte aplasia to prevent infectious diseases.
  • Stem cell therapy: for its immunomodulatory and anti-inflammatory activity. They are responsible for repopulating the bone marrow by their ability to differentiate into blood cells.
  • Hematopoietic growth factors: given as part of chemotherapy.
  • Immunoglobulin Therapy: May only provide temporary relief from bone marrow aplasia.
  • Antilymphocyte or antifungal globulin therapy: can eliminate certain aspects of the disease related to fungi.
  • Cyclosporin A: used as an immunosuppressant if the immune response is impaired.
  • Corticosteroids: steroid hormones.
  • Bone Marrow Transplantation: Only likely for young dogs with severe aplastic anemia and only if resources are available.

Prognosis of bone marrow aplasia in dogs

Canine medullary aplasia generally has a poor prognosis. It is a pathology in which, in many cases, the response to treatment is poor. Consequently, it can cause the death of our dog, especially if it does not respond to immunosuppression or the origin of the spinal aplasia is not detected. Fortunately, it is also relatively rare. It will need to be diagnosed by a qualified vet, one of the reasons why it is so important that we have regular vet checkups with our dog.

Does your dog have spinal aplasia? Do you want us to do a treatment together? Get in touch with us so we can help you.