Thrombocytopenia

Thrombocytopenia means a platelet count below 150 × 10⁹/L. Platelets are cell fragments made by megakaryocytes in the bone marrow. They adhere to injured vessel walls, become activated, and aggregate to form the initial platelet plug. A low count therefore disrupts primary haemostasis; it does not directly indicate a deficiency of clotting factors. The bleeding pattern often reveals which part of haemostasis is failing. Platelet-related bleeding is usually mucocutaneous: petechiae, purpura, easy bruising, epistaxis, gingival bleeding, heavy menstrual bleeding, hematuria, or gastrointestinal bleeding. Deep muscle haematomas and hemarthroses are more characteristic of a clotting-factor disorder, although severe thrombocytopenia can eventually cause bleeding in any tissue. The number matters, but it is not the whole assessment. Counts below 10 × 10⁹/L markedly increase the risk of spontaneous bleeding; counts below 20 × 10⁹/L are associated with clinically significant bleeding. A stable count of 25 × 10⁹/L in a patient without bleeding is a different clinical problem from a count falling from 180 to 70 × 10⁹/L in one day. Trend, active bleeding, medication effects, infection, liver disease, and an upcoming procedure...