Thrombocytosis is a characteristic of

• A. Disseminated intravascular coagulation
• B. Splenomegaly
• C. Polycythemia vera
• D. Idiopathic thrombocytopenic purpura

Answer: (C)

Thrombocytosis means an elevated platelet count, which is a hallmark of myeloproliferative disorders where the bone marrow overproduces blood cells. The classic condition among these options that includes increased platelets is polycythemia vera. This clonal hematopoietic stem cell disorder, often driven by a JAK2 mutation, leads to overproduction of all three cells lines, including a high platelet count, contributing to thrombotic risk from the thickened blood.

Disseminated intravascular coagulation, by contrast, uses up platelets and clotting factors, so platelets are usually low rather than high. Idiopathic thrombocytopenic purpura is an autoimmune destruction of platelets, also causing low counts. Splenomegaly can accompany various disorders and may influence platelet counts through sequestration, but it does not specifically define thrombocytosis. Thus, the condition most characteristically associated with thrombocytosis is polycythemia vera.