thrombocytopenias

Thrombocytopenia is a condition defined by a lower-than-normal platelet count in the blood, typically below 150,000 platelets per microliter. Platelets are essential for stopping bleeding, so reduced numbers raise the risk of bruising, petechiae, mucosal bleeding, and, in severe cases, intracranial hemorrhage.

Causes fall into categories based on mechanism: decreased production in the bone marrow (for example, aplastic anemia, leukemia, myelodysplastic syndromes), increased destruction or consumption (immune thrombocytopenia, drug-induced thrombocytopenia, infections, thrombotic microangiopathies), sequestration in an enlarged spleen (hypersplenism), or dilution after massive transfusion.

Common forms include immune thrombocytopenia (ITP), which can be primary or secondary; drug-induced thrombocytopenia; heparin-induced thrombocytopenia (HIT); and thrombotic microangiopathies such as thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). Neonatal or maternal alloimmune thrombocytopenia and pseudothrombocytopenia from in vitro clumping are other considerations.

Presentation and diagnosis typically start with a history and physical exam noting easy bruising, petechiae, or mucosal bleeding. Diagnostic workup includes a complete blood count and peripheral smear to confirm thrombocytopenia and exclude pseudothrombocytopenia, plus tests guided by suspicion of specific causes (coagulation studies, reticulocyte count, LDH, bilirubin, ADAMTS13 activity for TTP, drug screens, infection testing). Bone marrow examination is considered if marrow disease is suspected or features are atypical.

Management depends on cause and bleeding risk. Mild cases may be monitored. ITP is often treated with corticosteroids, IVIG, or anti-D, with options such as rituximab, splenectomy, or thrombopoietin receptor agonists for persistent disease. HIT requires stopping heparin and using an alternative anticoagulant. TTP/HUS requires urgent plasma exchange. Platelet transfusion is reserved for significant bleeding or procedures, as transfused platelets may be rapidly consumed in immune or microangiopathic states.