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Myxedema and Myxedema Coma in Dogs

Myxedema coma is a rare condition in dogs characterized by an under-functioning thyroid gland (hypothyroidism). Affected dogs become cold, extremely weak, and mentally dull/depressed. Animals with myxedema have a drop in metabolism, in the oxygen production in their cells, and in calorie production. This diseased condition has a high mortality rate. Affected animals may progress from depressed, to comatose, to dead in relatively short order. Successful treatment is reliant upon early recognition of the disorder and prompt and appropriate medical treatment.

The name myxedema refers to the swelling above the eyes, and in the jowls that these patients display. This edema occurs because of an increase in dermal ground substances in their skin (the jelly like material in which collagen bundles are based in the skin).

Myxedema coma has been most commonly reported in Doberman pinschers.

Symptoms and Types

• Weakness
• Lack of energy
• Low body temperature
• Low heart rate
• Slow breathing rate
• Collapse
• Myxedema of the face and jowls
• Itchy skin or a poor hair coat
• Possible bluish-purple gums
• Mental dullness/depression
• Secondary to severe hypothyroidism

Causes

• Severe primary hypothyroidism
• Infectious diseases
• Respiratory disease
• Central nervous system, or respiratory system depressants (anesthetics and tranquilizers)
• Heart failure
• Hypovolemia(not enough blood in the vessels, causing low blood pressure)
• Exposure to cold environmental temperatures

Diagnosis

Your veterinarian will perform a thorough physical exam on your pet, with a chemical blood profile, a complete blood count, a urinalysis and an electrolyte panel. A specific blood test for thyroxine levels (the thyroid gland hormone that regulates the metabolic rate) will indicate (along with clinical signs) for certain whether or not your pet is suffering from myxedema. You will need to give a thorough history of your pet's health, including a description of the onset of symptoms.

Chest and abdominal x-rays will also be taken to look for effusion (excess fluid) and swelling in your pet’s lungs.

Treatment

Your veterinarian will warm your pet with blankets in order to raise the body temperature to a healthy level. Warming your pet too quickly is very dangerous to its health, and must be done with care. Fluid therapy may also be administered. If your pet is having trouble breathing, it will be placed in an oxygen cage, but if it has not had enough oxygen for some time, it may be placed on a respirator. Appropriate medicine will be given to increase your pet’s metabolism, and your veterinarian will probably prescribe antibiotics as well.

Living and Management

Myxedema coma generally has a grave prognosis. Most patients who have died of this disease have died within a day of having begun treatment, even though their vital signs appeared to have improved.