Thrombocytopenia is the most common cause of spontaneous bleeding in dogs and is rare in cats. It is caused by a decrease in circulating platelet numbers as a result of one or more of the following abnormalities:
- Decreased platelet production – bone marrow disease, virus (FIV/FeLV/Parvo), chemotherapy drugs.
- Leukaemia may decrease platelet numbers due to the destruction of bone marrow architecture.
- Increased platelet destruction – IMTP, chemotherapy drugs, NSAID’s
- Platelet loss or consumption – haemorrhage, DIC, sepsis, vasculitis, splenic torsion
- Splenic sequestration (blood pooling in spleen) – hypersplenism (90% of circulating platelets become sequestrated in the spleen), severe hypothermia
- Tick-borne diseases – Babesia canis, ehrlichiosis, rocky mountain fever (USA)
- Secondary to other IM diseases i.e. immune mediated haemolytic anaemia (IMHA) or immune mediated poly arthritis (IMPA)
- Drug reactions – live virus vaccinations
- Neoplasia – lymphoma, haemangiosarcoma