Platelets and white blood cells are two of the main blood cell types in the body. Abnormal levels of these cells can be a sign of illness, disease or complications. Thrombocytopenia, or a low platelet count, can have serious consequences because platelets are required for blood clotting, and excess bleeding can occur if levels are decreased. A healthy platelet count is 150,000 or higher. Leucopenia or low white blood cell count is a decrease in leukocytes in the blood. White blood cells are important disease-fighting cells in the immune system, and low levels can cause infection and illness. Causes of low platelets and white blood cells include illness, disease, medication side effects and complications of cancer treatments.
Decreased platelet counts can occur due to an unhealthy and enlarged spleen. MayoClinic.com explains that the spleen is normally an important infection-fighting and blood filtering organ, but if it becomes enlarged it may trap too many platelets. This causes a decrease in the number of platelets in circulating blood, leading to serious bleeding disorders. As platelets live for only 10 days, the body is not able to produce enough to keep the platelet count high enough.
An infection, particularly viral and parasitic infections, can decrease white blood cell counts by destroying cells and damaging bone marrow, where blood cells are produced. Platelets are also produced in the bone marrow, and MayoClinic.com notes that the production of these cells is also suppressed by infection, leading to low platelet counts. A severe bacterial or viral and parasitic infection in the blood can also cause the destruction of platelets.
Chemotherapy cancer treatment is used to suppress rapidly multiplying cancer cells, but it can also damage healthy cells. When the bone marrow is affected, production of both white blood cells and platelets can be hindered, leading to decreased levels in the body. However, as MayoClinic.com notes, the effects of chemotherapy on bone marrow and other healthy organs are temporary, and platelet and white blood cell production return to normal levels some time after treatment is stopped.
Autoimmune disorders occur when the body's immune system attacks its own healthy tissue. This can decrease white blood cell and platelet counts in the body. If the disease targets bone, it can also damage the bone marrow and hinder the production of blood cells. Examples of common autoimmune diseases include allergies, rheumatoid arthritis and lupus.