A 22-year-old woman comes to the emergency department due to a nosebleed. She had a similar episode yesterday, but the bleeding stopped with prolonged local pressure. On review of systems, the patient has also had easy bruising for the past several months. She has no significant past medical history and takes no medications. On physical examination, her heart and lungs appear normal. The liver span is 8 cm and the spleen is not palpable. There are scattered ecchymoses over her arms and legs. Laboratory results are as follows: HIV and hepatitis C tests are negative. Which of the following is the most likely primary mechanism causing this patient's condition?

Question

A 22-year-old woman comes to the emergency department due to a nosebleed.  She had a similar episode yesterday, but the bleeding stopped with prolonged local pressure.  On review of systems, the patient has also had easy bruising for the past several months.  She has no significant past medical history and takes no medications.  On physical examination, her heart and lungs appear normal.  The liver span is 8 cm and the spleen is not palpable.  There are scattered ecchymoses over her arms and legs.  Laboratory results are as follows:  HIV and hepatitis C tests are negative.  Which of the following is the most likely primary mechanism causing this patient's condition?

Quizplus · Accepted Answer

This patient has recurrent epistaxis, ecchymoses, and marked thrombocytopenia (normal 150,000-400,000/mm³). She has a normal hematocrit, leukocyte count and differential, fibrinogen level, and prothrombin time/International Normalized Ratio. She takes no medications, and there is no obvious hepatosplenomegaly on physical examination. Taken together, these findings suggest an isolated acquired thrombocytopenia. Common causes of acquired thrombocytopenia include increased platelet consumption, sequestration, and/or destruction. In this patient, primary immune thrombocytopenic purpura (ITP) is the most likely diagnosis as, other than thrombocytopenia (with associated ecchymosis), her physical examination and laboratory findings are unremarkable. ITP is characterized by the autoimmune destruction of platelets by anti-platelet antibodies, likely IgG autoantibodies against the platelet membrane glycoproteins GPIIb/IIIa. In children, ITP is typically acute and self-limited, whereas it tends to run an insidious and chronic course in adults. A peripheral blood smear with isolated thrombocytopenia and no other platelet abnormalities would help confirm the diagnosis (megakaryocytes can sometimes be seen). Treatment involves systemic immunosuppression (corticosteroids). Secondary ITP is sometimes associated with HIV or hepatitis C infection. (Choice A) Bone marrow aplasia would cause pancytopenia. It is unlikely that this patient's thrombocytopenia is due to bone marrow failure as the peripheral counts of the hematopoietic cell lines, other than platelets, are normal. Common causes of aplastic anemia include parvovirus and Epstein-Barr virus infections, high-dose chemotherapy, and radiation. (Choice B) Malignant infiltration of the bone marrow would be expected to cause pancytopenia and extramedullary hematopoiesis within the liver and spleen, leading to hepatosplenomegaly. (Choice C) If this patient were experiencing accelerated platelet consumption due to disseminated intravascular coagulation, the plasma fibrinogen level would be decreased and the prothrombin time would be elevated due to clotting factor consumption. (Choice E) Splenic sequestration of platelets typically occurs in disorders that produce splenomegaly, such as portal hypertension; the platelet count usually remains >30,000/mm³, and abnormal bleeding generally does not occur. Although platelets can undergo splenic sequestration in ITP, the primary mechanism responsible for the thrombocytopenia is immune destruction. (Choice F) In von Willebrand disease, platelet function is impaired because von Willebrand factor, which normally facilitates platelet binding to damaged endothelium, is deficient. The platelet count would be normal (unlike in this patient), and the bleeding time and partial thromboplastin time would be prolonged. Educational objective: Autoimmune platelet destruction is a common cause of thrombocytopenia and should be suspected in patients with ecchymoses, petechiae, mucosal bleeding, and no other obvious causes of thrombocytopenia (eg, medications, bone marrow failure).

A 22-Year-Old Woman Comes to the Emergency Department Due to a Nosebleed