Snapshot A 42-year-old man presents to his primary care physician's office for easy bruising and gingival bleeding. He reports his symptoms began one day prior to presentation and has never occurred before. Medical history is significant for a recently diagnosed hepatitis C infection. On physical exam, there is mild bleeding of the gums. There are petechiae throughout the chest, arms, and legs. There is no evidence of splenomegaly on abdominal exam. A complete blood count is significant for a platelet count of 24,000/μL and peripheral blood smear demonstrates enlarged platelets. He is started on corticosteroids. 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 systemic lupus erythematosus antiphospholipid syndrome infection HIV hepatitis C virus malignancy chronic lymphocytic leukemia 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 in patients with a platelet count > 30,000/μL and no bleeding Medical corticosteroids indication initial treatment for patients with a platelet count < 30,000/μL intravenous immunoglobulins (IVIG) indication for patients with a platelet count < 30,000/μL who have contraindications to corticosteroids, are refractory to corticosteroid treatment, or are bleeding or have a high risk of bleeding that will need a rapid increase in platelet count Operative splenectomy indication second-line treatment for patients with refractory ITP Complications Fatal hemorrhage