Which rare blood disorder is characterized by widespread microvascular thrombosis causing thrombocytopenia and hemolytic anemia?

• A. DIC
• B. HUS
• C. ITP
• D. TTP (thrombotic thrombocytopenic purpura)

Answer: (D)

Thrombotic thrombocytopenic purpura is a microangiopathic process where small-vessel clots form throughout the circulation, consuming platelets and shearing red cells to produce hemolytic anemia. The key driver is severe deficiency of the enzyme ADAMTS13, which normally cleaves ultra-large von Willebrand factor multimers; without it, these multimers cause widespread platelet aggregation and microthrombi in tiny vessels. This leads to the combination of low platelets and hemolysis, often with neurological symptoms and sometimes renal involvement. Coagulation tests (PT, PTT, fibrinogen, D-dimer) are typically normal, because the problem is platelet consumption from microthrombi rather than a primary activation of the coagulation cascade. This helps distinguish it from disseminated intravascular coagulation, where coagulation tests are abnormal; from hemolytic uremic syndrome, which has MAHA and thrombocytopenia but usually rushes toward renal failure without the classic ADAMTS13 deficiency and neurological signs; and from immune thrombocytopenic purpura, where there is isolated thrombocytopenia without hemolysis or microangiopathy.