A previously healthy 30-year-old woman is admitted to the hospital. She complains of a rash over her ankles that started 2 weeks ago and slowly spread up to her knees. The patient has no other medical problems and takes no regular medications. Her vital signs are within normal limits. Physical examination shows fine petechiae and purpura around her ankles and lower legs. There is no lymphadenopathy or hepatosplenomegaly. Laboratory results are as follows:
Peripheral blood smear shows thrombocytopenia. After reviewing the laboratory results, the admitting resident orders 6 units of random donor platelet transfusion. The following day, the platelet count is 10,000/µL.
Which of the following is the most likely cause of the drop in the platelet count?

Question

A previously healthy 30-year-old woman is admitted to the hospital.  She complains of a rash over her ankles that started 2 weeks ago and slowly spread up to her knees.  The patient has no other medical problems and takes no regular medications.  Her vital signs are within normal limits.  Physical examination shows fine petechiae and purpura around her ankles and lower legs.  There is no lymphadenopathy or hepatosplenomegaly.  Laboratory results are as follows:
 Peripheral blood smear shows thrombocytopenia.  After reviewing the laboratory results, the admitting resident orders 6 units of random donor platelet transfusion.  The following day, the platelet count is 10,000/µL.
Which of the following is the most likely cause of the drop in the platelet count?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bf61_2dae_8f63_a9156edc3352_MD0005_00 This patient's lower-extremity petechiae and isolated thrombocytopenia suggest immune thrombocytopenic purpura (ITP). A presumptive diagnosis of ITP can be made when the history, physical examination, complete blood count, differential count, and peripheral blood smear show isolated thrombocytopenia without any obvious causes. ITP is due to platelet destruction by antiplatelet autoantibodies, which are most often directed against membrane proteins (eg, GPIIb/IIIa). Circulating platelets are rapidly removed by the autoantibodies, limiting the role of platelet transfusions. (Choice B) Disseminated intravascular coagulation (DIC) is a consumptive coagulopathy (leading to both bleeding and thrombosis) usually associated with sepsis, trauma, malignancy, or obstetric complications. DIC typically causes an elevated D-dimer (due to accelerated fibrinolysis), prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT) (due to depletion of clotting factors), often with low fibrinogen (due to consumption). This patient's normal D-dimer, PT, and aPTT make DIC less likely. (Choice C) Hypersplenism, whether from portal hypertension or other causes of splenomegaly, is characterized by excessive platelet sequestration in the spleen. The platelet count usually remains >30,000/µL and the overall platelet mass and function remain normal. Clinical bleeding usually does not occur in these patients. (Choice D) Septicemia is characterized by abnormal vital signs (eg, tachycardia, hypotension), usually with an elevated leukocyte count. This patient's stable vital signs make this unlikely. (Choice E) Thrombotic thrombocytopenic purpura is characterized by thrombocytopenia and microangiopathic hemolytic anemia, which manifests as schistocytes on peripheral smear and elevated lactate dehydrogenase. Other features may include acute renal failure, fever, and neurologic abnormalities. schistocytes Educational objective: Immune thrombocytopenic purpura is characterized by normal coagulation factors and isolated thrombocytopenia without any obvious etiology. It is due to antiplatelet autoantibodies that remove circulating platelets. References: Immune thrombocytopenia. (http://www.ncbi.nlm.nih.gov/pubmed/23714309)

A Previously Healthy 30-Year-Old Woman Is Admitted to the Hospital