Dogs that are diagnosed with a condition known as thrombocytopenia will have problems with both bleeding and bruising due to a low number of platelets in the blood, which will prevent the blood from clotting. This condition can be fatal, especially if the dog is seriously injured and has internal or external bleeding that cannot be stopped. In addition if the dog's platelet count drops below a certain level they can start spontaneously bleeding internally which is almost always a fatal condition.

There are two different types of thrombocytopenia. The first type is called immune-mediated thrombocytopenia and is hereditary in nature. The breeds most commonly seen with this inherited condition include Poodles, American Cocker Spaniels and Old English Sheepdogs. It is much more prevalent in females, which is one of the key factors in determining that it is a sex-linked genetic condition.

Blood platelets are produced in bone marrow in dogs and humans. Dogs with immune-mediated thrombocytopenia actually suppress their own body's ability to produce platelets, resulting in bleeding that does not clot or stop on its own. In most cases of immune-mediated thrombocytopenia there may be additional stressors on the dog when the condition occurs. In females often their reproductive hormones make the condition worse so spaying at an early age is highly recommended.

The other cause of thrombocytopenia is due to other illnesses or conditions that cause either a reduced production of platelets, incorrect storage of the platelets in other body organs and breakdown of existing platelets in the body. Diseases such as cancers, failure of the liver or kidney or reduced functioning of these organs, or even the use of different types of medications can all cause blood platelets to decrease in the system. Tick bites can also cause the condition. Rocky Mountain Spotted Fever is caused by bacteria in the tick saliva and will lead to thrombocytopenia. Treatment for ticks and immediate removal of any ticks is essential to minimizing the chances of getting the condition through bites.

The symptoms of thrombocytopenia include small bruises or red or bluish spots under the skin, nosebleeds, blood in the urine or feces, red spots in the eyes, bleeding or red spots on the gums and fatigue. A blood test is required to confirm the diagnosis and is done by simply counting the platelets. A normal dog will have 60,000 platelets per microliter of blood whereas dogs with thrombocytopenia will have less than 40,000.

Treatment includes corticosteriods to stop the immune system from breaking down the existing platelets as well as antibiotics to help the overall systems in functioning. The key is to find out the root cause of the platelet destruction or low numbers and address that issue as well. In cases where the disease is inherited whole blood transfusions may be required if the dog starts to hemorrhage internally or the external bleeding cannot be stopped. Immediate emergency treatment is needed to prevent loss of life in these conditions.