An 18-year-old woman presented to the emergency department for evaluation of a petechial rash and heavy menstrual bleeding following a recent bout of exudative pharyngitis and posterior cervical lymphadenopathy. Her platelet count is 5 x 109/L and her hemoglobin is 9 g/dL. Her creatinine is normal, and her manual blood smear is remarkable for few platelets and no schistocytes. What is the differential diagnosis?
Find the diagnosis and case discussion on p. 10.
Diagnosis: Immune Thrombocytopenia
Immune thrombocytopenia (ITP), formerly called immune or idiopathic thrombocytopenic purpura, is an immune-mediated disease defined by isolated thrombocytopenia of less than 100 x 109/L in the absence of hemolytic anemia or any other known cause for the thrombocytopenia. It is classified as primary (idiopathic) or secondary (an identifiable medication or underlying process drives platelet destruction) and also as acute, persistent, or chronic. (Blood 2009;113:2386.)
ITP is thought to occur when IgG autoantibodies are directed against platelet membrane glycoproteins, causing a destructive thrombocytopenia. New evidence suggests that a degree of bone marrow suppression also occurs. (Blood 2011;117:4190.) The incidence is thought to be 3.3 cases per 105 adults per year. (Am J Hematol 2010;85:174.) The inciting causes of ITP are diverse, and include medication, vaccination, infection, rheumatologic disease, immune deficiency, and hematologic malignancy. (Autoimmun Rev 2014;13[4-5]:577.) Increased age is thought to be an independent factor for increased bleeding. (Am J Hematol 2011;86:980.)
Patients most commonly present with bleeding, typically from mucocutaneous areas. The rash is purpuric or petechial, and is often in dependent areas or areas under constriction like the axilla. Severe bleeding or hemorrhage is usually rare. (Emerg Med Clin N Am 2014;32:649.)
The diagnostic evaluation of ITP involves ruling out other etiologies of thrombocytopenia. A complete blood count with peripheral smear, renal function panel, reticulocyte count, type and screen, Coombs test, DIC panel, and pregnancy test are useful to identify other diagnoses because ITP is a diagnosis of exclusion. Hepatitis C and HIV testing should also be obtained because these can cause secondary ITP. A routine bone marrow exam for typical ITP is not recommended. (Blood 2011;117:4190.)
The differential for ITP includes non-immune causes of thrombocytopenia, including the thrombotic microangiopathies under which thrombotic thrombocytopenic purpura and hemolytic uremic syndrome are categorized. The thrombotic microangiopathies are characterized by widespread platelet thrombi and microvasculature occlusion resulting in blood cell damage and organ damage. (N Engl J Med 2014;371:654.) Disseminated intravascular coagulation, heparin-induced thrombocytopenia, lymphoma, and leukemia must be considered as well as HELLP syndrome and thrombocytopenia of pregnancy. (Autoimmun Rev 2014;13[4-5]:577.)
Immune suppression with oral or IV steroids is currently recommended for asymptomatic adult patients with platelet counts less than 30 x 109/L or for severe bleeding. Time to treatment response is variable from days to weeks. Acute exacerbations can develop into persistent or chronic ITP. (Blood 2009;113:2386.) Studies have found that durable remission can be challenging with steroids alone (N Engl J Med 2010;363:1959), and IVIG or anti-D therapy may be warranted in select patients in consultation with a hematologist. Rituximab, splenectomy, and thrombopoiesis-stimulating agents are not first-line therapies, but should be considered in severe or prolonged cases. (Blood 2011;117:4190.) Some hematologists still prefer bone marrow biopsy before glucocorticoid treatment in children because of the increased incidence of acute lymphoblastic leukemia. Treatment of children with ITP is controversial, and often involves observation only, regardless of platelet counts because of lower bleeding risk. (Blood 2009;113:2386.)
This patient was treated with IV steroids and two days of IVIG for persistent heavy vaginal bleeding and anemia requiring transfusion. She was transitioned to an oral steroid taper for four weeks and was doing well at follow-up. Ultimately, it was thought she had secondary acute ITP associated with the Epstein-Barr virus.
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