Snapshot A 38-year-old man presents to his primary care physician's office for episodes of epistaxis and gingival bleeding. He reports his symptoms began one day prior to presentation and has never occurred before. He denies starting any new medications. Social history is notable for current intravenous drug use. On physical exam, there is blood in the nares and mild bleeding of the gums. There are petechiae distal to where the blood pressure cuff was placed. Abdominal exam is unremarkable. A complete blood count is significant for a platelet count of 28,000/μL and peripheral blood smear demonstrates enlarged platelets. Introduction Clinical definition acquired immune-mediated destruction of otherwise normal platelets Classification primary immune thrombocytopenia (ITP) immune-mediated thrombocytopenia without an underlying condition secondary ITP immune-mediated thrombocytopenia with an underlying condition (e.g., HIV infection) Epidemiology demographics 1-7 years of age commonly in children Etiology primary ITP unknown secondary ITP autoimmune disorders login to view 2 more bullets infection login to view 2 more bullets malignancy login to view 1 more bullet vaccinations Pathogenesis IgG antibodies directed against platelet membrane glycoproteins such as GPIIb/IIIa a type II hypersensitivity reaction Presentation Symptoms asymptomatic bleeding symptoms gingival bleeding epistaxis Physical exam petechiae purpura ecchymosis atypical to have a palpable spleen Studies Making the diagnosis primary ITP isolated thrombocytopenia (e.g., < 100,000/μL) without a known cause secondary ITP isolated thrombocytopenia (e.g., < 100,000/μL) with an underlying condition (e.g., positive for HIV infection) Differential Hypersplenism distinguishing factor splenomegaly Liver disease distinguishing factor elevated transaminases and hepatosplenomegaly coagulation abnormalities may be present Microangiopathic hemolytic process (e.g., thrombotic thrombocytopenic purpura) distinguishing factor schistocytes are appreciated on peripheral blood smear Treatment Conservative observation indication login to view 1 more bullet Medical corticosteroids indication login to view 1 more bullet intravenous immunoglobulins (IVIG) indication login to view 1 more bullet Operative splenectomy indication login to view 1 more bullet Complications Fatal hemorrhage