Thrombocytosis

Chronic thrombocytosis

Reactive thrombocytosis

Secondary thrombocytosis

Thrombocythemia, NOS

Thrombocytosis and thrombocythemia are conditions in which the blood has a higher than normal number of platelets.

Thrombocytosis is caused when another disease or condition causes a high platelet count. This condition is often called secondary or reactive thrombocytosis.

Thrombocythemia is when the cause of a high platelet count isn't known. The condition sometimes is called primary or essential thrombocythemia.

Thrombocytosis or thrombocythemia by themselves are not reportable. If they are referred to as primary/essential thrombocytosis or primary/essential thrombocythemia, then this is reportable (see 9962/3).

For more information: http://www.nhlbi.nih.gov/health/health-topics/topics/thrm/