Chapter 25: Bleeding Disorders Caused by Vascular and Platelet Abnormalities

Bleeding Disorders Caused by Vascular and Platelet Abnormalities establishes a primary distinction between these disorders—which typically present as mucosal bleeding and skin purpura—and coagulation factor deficiencies that often result in deep tissue or joint hemorrhages. Vascular disorders are categorized into inherited forms, such as hereditary hemorrhagic telangiectasia involving endoglin mutations and connective tissue defects like Ehlers–Danlos syndrome, and acquired conditions including senile purpura, vitamin C deficiency (scurvy), and Henoch–Schönlein syndrome, an IgA-mediated vasculitis. A major portion of the chapter is dedicated to thrombocytopenia, which can result from decreased bone marrow production, increased peripheral destruction, or splenic sequestration. Immune thrombocytopenic purpura (ITP) is detailed as a significant autoimmune condition where IgG antibodies target platelet glycoproteins, leading to their premature removal by the reticuloendothelial system. Treatment modalities for ITP have evolved beyond corticosteroids and splenectomy to include rituximab and thrombopoietin-receptor agonists that stimulate megakaryocyte production. The text also examines critical microangiopathic syndromes like thrombotic thrombocytopenic purpura (TTP), caused by a deficiency in the ADAMTS13 enzyme, which leads to the formation of occlusive platelet thrombi. Furthermore, the chapter covers qualitative platelet defects, distinguishing between rare hereditary syndromes such as Glanzmann’s thrombasthenia and Bernard–Soulier syndrome and common acquired causes, most notably the inhibitory effects of antiplatelet medications like aspirin and clopidogrel. Diagnostic approaches are emphasized, utilizing peripheral blood film examination to exclude artifacts like pseudothrombocytopenia, alongside bone marrow analysis and specialized platelet aggregation studies to pinpoint specific functional or production failures.