What causes a high platelet count and anemia?

My son has had a high platelet count and anemia for years. We have him tested twice a year now, but no one can give me a diagnosis,cause, or reason to keep testing him. They just say he does not need to get dehydrated. Has Anyone ever heard of this?

Thrombocythemia

In thrombocythemia, too many platelets are produced. Excessive clotting or bleeding may result.

In the bone marrow, the cells that become platelets increase in number (proliferate). Why the cells proliferate is unknown. But the result is too many platelets. If there are too many platelets, blood clots can form spontaneously. Clots may block blood vessels, especially small ones. Sometimes in thrombocythemia, platelets do not function normally. Then, excessive bleeding may occur.

Causes

Usually, no cause can be identified. Other disorders that can cause thrombocythemia include iron deficiency anemia, cancer that has spread (metastasized), leukemia, lymphoma, polycythemia vera, and rheumatoid arthritis.

This is the closest diagnosis I can make. However this usually only occurs in 50 year olds, not children. Hope this helps.