Thrombocytopenia

Dogs with thrombocytopenia have a low number of platelets in their blood. Platelets are cell fragments, produced from the bone marrow, which travel around the body in the bloodstream. They help to prevent bleeding by clumping together to seal broken blood vessels. Dogs with low numbers of platelets are therefore at increased risk of bleeding.

Low platelet numbers can occur as a result of three processes:

1. Decreased production of platelets by the bone marrow as a result of:

2. Increased destruction of platelets in the blood as a result of:

3. An increase in the number of platelets taken out of the bloodstream as a result of:

Symptoms include small red spots on the skin and gums (called petechiae) as a result of pinpoint bleeding, and sometimes larger areas of bruising over the body. Affected dogs may have blood in their urine, faeces, or vomit. The blood can either be dark or bright red. They may also bleed from their noses or gums. Blood loss as a result of an increase in bleeding can cause anaemia (loss of red blood cells) resulting in pale gums, increased breathing rate, lethargy and weakness. Dogs with thrombocytopenia may not show any clinical symptoms.

Thrombocytopenia can be diagnosed from a blood test. Your dog’s blood sample will be analysed by a machine which will count the number of platelets in the sample. Sometimes the results will need to be checked by a vet or vet nurse, who will visualise the blood sample under a microscope and perform a manual count of the number of platelets. This is because the “quick” machine test for platelets sometimes miscounts.

Your vet will want to perform further diagnostic tests to work out the cause of the thrombocytopenia. For example, they may want to perform tests to detect infectious diseases, perform an ultrasound scan to check for enlargement of the spleen or perform a bone marrow sample test.

It is important to let your vet know if you have travelled abroad with your dog so that they can test for any diseases found in other countries such as tick-bourne diseases.

Patients who have lost large amounts of blood as a result of thrombocytopenia may require a blood transfusion. A drug called Vincristine (usually used for chemotherapy) can also be administered to the patient as a one-off dose; it stimulates platelet production from the bone marrow. Your vet will be best placed to decide on the treatment appropriate for your dog’s condition, however, as there are risks with using this drug.

It is important to treat the underlying cause of the condition, treatment options will vary depending on the cause.

Immune-mediated thrombocytopenia is treated using medications which suppress the immune system, making it less likely to attack the body's own platelets. The most commonly prescribed medication is a steroid called prednisolone. Treatment usually lasts several months until the patient starts producing normal numbers of platelets.

Treatment of the underlying condition, where possible, should reduce the severity of thrombocytopenia or prevent recurrence.

It is possible for dogs to suffer from other bleeding disorders which do not affect their platelet numbers. Von Willebrand’s disease is an example of an inherited disorder which can cause increased bleeding in dogs - please see our factsheet on von Willebrand’s disease for further information.