Thin blood, also called thrombocytopenia, is caused by reduced production of platelets, enhanced degradation or consumption of platelets and increased sequestration of platelets by the spleen, reports MedicineNet. Each of these causes can occur due to different reasons such as infections, cancer treatment and disturbances in the immune system.
Decreased production of platelets may occur because of viral infections such as mumps and chickenpox and aplastic anemia in which the blood does not generate platelets and other blood cells, says MedicineNet. Leukemia, bone marrow cancer and cancers of other organs that invade the bone marrow can also lead reduced platelet generation. Chemotherapy drugs and other medications, vitamin B12 and folic acid deficiency and chronic alcohol consumption either directly inhibit platelet generation or suppress bone marrow function.
Increased degradation of platelets occurs due to immunologic disturbances caused by medications such as sulfonamide antibiotics and heparin and blood transfusions, states MedicineNet. Sometimes, the immune system may attack platelets for unknown reasons and reduce their count. Blood vessel injury or inflammation, sepsis and thrombotic thrombocytopenic purpura lead to increased platelet consumption.
If the spleen becomes enlarged owing to a disorder, it tends to harbor greater than the normal quantities of platelets leading to reduced platelet circulation, states Mayo Clinic. In rare cases, thin blood or thrombocytopenia may be present in neonates owing to certain genetic conditions, notes MedicineNet.