A 30-year-old female is admitted with neurological symptoms. Laboratory results show severe anemia, thrombocytopenia, schistocytes, and markedly decreased ADAMTS-13. What is the most likely diagnosis?

• A. Thrombotic thrombocytopenic purpura
• B. Idiopathic thrombocytopenic purpura
• C. Hemolytic uremic syndrome
• D. von Willebrand disease

Answer: (A)

The key idea is that a severe deficiency of the enzyme ADAMTS-13 causes thrombotic microangiopathy. ADAMTS-13 normally cleaves ultra-large von Willebrand factor multimers; when it’s markedly reduced, these ultra-large multimers promote widespread platelet clumping in very small vessels. This forms microthrombi that use up platelets and shear passing red blood cells, producing schistocytes and microangiopathic hemolytic anemia. The result is both thrombocytopenia and hemolysis, with neurologic symptoms arising from microvascular obstruction in the brain. The combination of neuro symptoms, schistocytes on blood smear, thrombocytopenia, and markedly decreased ADAMTS-13 is characteristic of thrombotic thrombocytopenic purpura.

In contrast, hemolytic uremic syndrome typically shows prominent kidney involvement and often occurs after a diarrheal illness, without the characteristic severe ADAMTS-13 deficiency; idiopathic ITP presents with isolated low platelets and no schistocytes or MAHA; von Willebrand disease causes mucocutaneous bleeding and usually not MAHA or low platelets.