Platelets are a type of blood cell that play an important role in blood clotting. Platelets are made in the bone marrow, and is the organ that produces all types of blood cells. The condition can develop when the bone marrow stops regulating its production of platelets and other blood cells, often as a result of a mutation or other type of injury to the marrow. Conditions that can cause the bone marrow to produce too many platelets include infections, surgery, iron deficiency, and prior removal of the spleen.
If no cause is found, it may be necessary to take a microscopic look at your son's bone marrow. Usually this requires a procedure called a bone marrow biopsy. Special tests may be done to look for conditions that would cause your bone marrow to make too many cells.
Untreated the risk is abnormal bleeding and abnormal blood clotting. Since the risk of abnormal clotting is higher than the risk of bleeding, and since blood clots can be life threatening, low doses of aspirin are often used to "thin" the blood and prevent clots.