Numerical abnormalities of platelets thrombocytopenia
Defines a platelet count <150 x 109/L. May be due either to decreased bone marrow production of platelets or to increased destruction or sequestration of platelets from the circulation (or both). Platelet counts >100 x 109/L are not usually associated with any haemorrhagic problems. Purpura, easy bruising and prolonged post-traumatic bleeding are increasingly common as the platelet count falls <50 x 109/L. Although there is no platelet count at which a patient definitely will or will not experience spontaneous haemorrhage the risk is greater in patients with a platelet count <20 x 109/L and increases further in those with a count <10 x 109/L.