A 37-year-old woman has noted an excessively heavy menstrual flow each of the past 6 months. She also has noticed increasing numbers of pinpoint hemorrhages on her lower extremities in the past month. Physical examination shows no organomegaly or lymphadenopathy. CBC shows hemoglobin of 14.2 g/dL, hematocrit of 42.5%, MCV of 91 mm3, platelet count of 15,000/ mm3, and WBC count of 6950/ mm3. On admission to the hospital, she has melena and after a transfusion of platelets, her platelet count does not increase. Which of the following describes the most likely basis for her bleeding tendency?

This patient's bleeding tendency is caused by a low platelet count. She most likely has idiopathic chronic immune thrombocytopenic purpura (ITP), in which platelets are destroyed in the spleen after being coated with antibodies to platelet membrane glycoproteins IIb-IIIa or Ib-IX. These antibodies coat both the patient's platelets and any transfused platelets. Because the spleen is the major source of the antibody and the site of platelet destruction, a splenectomy can be beneficial if corticosteroid therapy is not. There is no defect in the production of platelets. Platelet functions are normal in ITP. Chronic blood loss would not lead to thrombocytopenia when normal bone marrow function is present. Abnormal platelet-endothelial interactions are more likely to cause thrombosis. Suppression of pluripotent stem cells gives rise to aplastic anemia, which is accompanied by pancytopenia.