What causes thrombocytosis?

Thrombocytosis, a low platelet count, is caused by medical conditions that result in bone marrow not producing enough platelets, the destruction of platelets in the bloodstream or an enlarged spleen or liver, according to MedlinePlus. Platelets are essential because they allow blood to clot, which prevent excessive bleeding.

Medical conditions that impact the production of platelet by bone marrow include aplastic anemia, cancer of bone marrow, liver cirrhosis, folate or vitamin B-12 deficiency and myelodysplastic syndrome, according to MedlinePlus. Some examples of medical conditions that can result in the destruction of platelets in the bloodstream are disseminated intravascular coagulation and immune thrombocytopenic purpura.