Thrombocytosis
Thrombocytosis is a high platelet count>450×109/L. It may be secondary to another pathological process or it may be due to a myeloproliferative disorder.
Symptoms and Signs
History of trauma, blood loss, surgery, splenectomy, chronic inflammatory disease. Infection and malignancy. Increased platelet count at routine blood test. Episodes of spontaneous arterial or venous thrombosis, e.g. stroke, DVT, venous thromboembolism. Hepatosplenomegaly.
Investigations
■ FBC
Platelets ↑. Hb ↓ (iron deficiency anaemia). Hb ↑ (polycythaemia rubrum vera). MCV ↓ (iron deficiency anaemia). PCV ↑ (polycythaemia rubrum vera). WBC ↑ (infection, chronic myeloid leukaemia).
■ Blood film
Microcytic hypochromic anaemia in iron deficiency. Thrombocytosis, giant platelets, platelet clumping, megakaryocyte fragments in essential thrombocythaemia.
■ ESR
Chronic inflammation. Malignancy. ESR very high in myeloma.
■ Serum iron and TIBC
Serum iron ↓ TIBC ↑ in iron deficiency.
■ Serum ferritin
Reduced in iron deficiency. Not affected by chronic disease.
■ Bone marrow
Essential thrombocythaemia – hypercellularity, increased megakaryocytes, large megakaryocytes. Polycythaemia rubrum vera – increased cellularity due to hyperplasia for erythropoietic cells, granulocytopoietic cells and megakaryocytes. Chronic myeloid leukaemia – marked hypercellularity due to myeloid hyperplasia. Myelofibrosis – ‘dry tap’ (aspiration unsuccessful).
