There are three main factors that can lower the platelet count, and hence cause thrombocytopenia. These include:
1) Reduced production of platelets in the bone marrow – caused by an enlarged spleen which can result from various disorders.
2) Increased breakdown or trapping of platelets in the spleen or liver - caused by diseases such as leukemia or anemia, viral infections like HIV, chemotherapy drugs, toxins or excessive consumption of alcohol.
3) Increased breakdown or trapping of platelets in the bloodstream – caused by a number of conditions including bacteria in blood, pregnancy, medication, autoimmune diseases, idiopathic thrombocytopenic purpura and thrombotic thrombocytopenic purpura.