Which condition is primarily an isolated autoimmune destruction of platelets, presenting with mucocutaneous bleeding and normal coagulation studies?

Which condition is primarily an isolated autoimmune destruction of platelets, presenting with mucocutaneous bleeding and normal coagulation studies?

• A. DIC
• B. Immune thrombocytopenic purpura
• C. Von Willebrand disease
• D. Hemophilia A

Answer: (B)

This question hinges on understanding cases where the bleeding is due to too few platelets rather than a problem in the coagulation cascade. When autoantibodies attack platelets, the result is a reduced platelet count with mucocutaneous bleeding—petechiae, purpura, easy bruising, nosebleeds, and gum bleeding—while the coagulation tests remain normal because the clotting factors and the cascade are intact. Immune thrombocytopenic purpura arises from antibodies targeting platelet surface proteins (often glycoproteins IIb/IIIa or Ib-IX), marking platelets for destruction by the spleen. Since the issue is the number of functional platelets, not a deficiency or dysfunction of the coagulation factors, PT and aPTT stay within the reference range. This pattern distinguishes it from other bleeding disorders: conditions like DIC involve widespread activation of coagulation with consumption of platelets and coagulation factors, leading to abnormal PT/aPTT; von Willebrand disease affects platelet adhesion and often shows abnormal platelet function tests and sometimes prolonged aPTT due to factor VIII involvement; hemophilia A is a deficiency of factor VIII and presents with deep, tendon, or joint bleeding and an abnormal aPTT.

This question hinges on understanding cases where the bleeding is due to too few platelets rather than a problem in the coagulation cascade. When autoantibodies attack platelets, the result is a reduced platelet count with mucocutaneous bleeding—petechiae, purpura, easy bruising, nosebleeds, and gum bleeding—while the coagulation tests remain normal because the clotting factors and the cascade are intact.

Immune thrombocytopenic purpura arises from antibodies targeting platelet surface proteins (often glycoproteins IIb/IIIa or Ib-IX), marking platelets for destruction by the spleen. Since the issue is the number of functional platelets, not a deficiency or dysfunction of the coagulation factors, PT and aPTT stay within the reference range. This pattern distinguishes it from other bleeding disorders: conditions like DIC involve widespread activation of coagulation with consumption of platelets and coagulation factors, leading to abnormal PT/aPTT; von Willebrand disease affects platelet adhesion and often shows abnormal platelet function tests and sometimes prolonged aPTT due to factor VIII involvement; hemophilia A is a deficiency of factor VIII and presents with deep, tendon, or joint bleeding and an abnormal aPTT.