Mr 2.24.14


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Mr 2.24.14

  1. 1. Immune thrombocytopenic purpura SAMREEN RAZA, MD PGY-3
  2. 2. Immune thrombocytopenic purpura  There are only two criteria required in order to make this diagnosis:  1. Isolated thrombocytopenia is present – rest of blood count is normal including peripheral smear  2. Clinically apparent associated conditions absent (eg, systemic lupus erythematosus, antiphospholipid syndrome, chronic lymphocytic leukemia)  Patients with these associated conditions are described as having "secondary immune thrombocytopenia  Herbal supplements and drugs not considered part of etiology
  3. 3. Pathogenesis  Related to a combination of increased platelet destruction along with inhibition of megakaryocyte platelet production via the production of specific IgG autoantibodies by the patient's B cells, most often directed against platelet membrane glycoproteins such as GPIIb/IIIa  Inciting events - etiology of ITP is unclear, but is thought to include genetic as well as acquired factors  Some cases of ITP are associated with a preceding viral infection:  Resulting anti-viral antibodies cross-react with platelet glycoproteins  Infection with HIV, HCV, CMV and VZV may be associated with such antibodies therefore cause secondary ITP.  Alterations in the immune response might induce loss of peripheral tolerance and promote the development of self-reactive antibodies  Abnormalities in the immune system may predispose to the development of ITP
  4. 4. Incidence  Incidence greater in children than adults  Danish study from 1973 to 1995 estimated annual incidence of ITP among adults to be 22 per million per year, using a platelet count cutoff of 50,000/microL  Incidence rose during the study period due to increased recognition of asymptomatic patients  Among adults with ITP, approx 70% are women and 72% of these women are less than 40 years of age  The Denmark survey reported a sex difference in the incidence of ITP only for those <60 years of age  Generalizability?
  5. 5. Physical examination features  Mucocutaneous features related to thrombocytopenia and bleeding  Not visceral hematomas which are characteristic of coagulation disorders eg hemophilia  Petechiae, purpura, ecchymoses  Epistaxis, gingival bleeding, menorrhagia  Overt gastrointestinal bleeding and gross hematuria are rare  Intracranial hemorrhage – very rare  The clinical manifestations of thrombocytopenia vary with age  Patients may have more severe bleeding manifestations including GI bleeding or ICH due to comorbidities such as hypertension
  6. 6. Diagnostic testing  Peripheral smear — Examination of the blood smear may provide evidence for other causes of thrombocytopenia eg presence of schistocytes  Examination of the peripheral blood smear is essential to exclude pseudothrombocytopenia due to the artifact of platelet agglutination induced by the standard blood count anticoagulant, EDTA  EDTA-dependent agglutinins are present in approximately 0.1% people in the general population  naturally occuring platelet antibody against normally concealed epitope on GpIIb/IIIa which becomes exposed by EDTA-induced dissociation of GpIIb/IIIa  You can make a presumptive diagnosis based on history, physical examination, CBC and examination of peripheral blood smear with isolated thrombocytopenia  H pylori infection – generally do not screen for this in patients with mild or moderate thrombocytopenia  Can do breath test or fecal antigen testing only in patients if ITP is chronic or refractory or if positive test would change management
  7. 7. Other causes Beverages and herbal remedies that can cause thrombocytopenia include:  Quinine  Tonic water  Sulfonamides including sulfamethoxazole  Heparin
  8. 8. Antiplatelet antibodies The American Society of Hematology ITP Practice Guidelines do not recommend antiplatelet antibody studies in patients thought to have ITP No evidence that antiplatelet antibody studies are important for diagnosis of ITP
  9. 9. Differential diagnosis TTP/HUS DIC Gestational thrombocytopenia Drugs Infection Hypersplenism Myelodysplasia Congential thrombocytopenias
  10. 10. Inherited platelet disorders  von Willebrand disease type 2B: with greater than expected bleeding for the degree of thrombocytopenia  Wiskott-Aldrich syndrome and its variant, X-linked thrombocytopenia, with small platelets and recurrent infections  Alport syndrome (hereditary nephritis) variants, with giant platelets, renal failure, and hearing loss  May-Hegglin anomaly, with giant platelets and Döhle bodies in granulocytes, and other manifestations of MYH9 gene mutations (the gene encoding the nonmuscle myosin heavy chain IIA)  Fanconi syndrome, with short stature, anemia, and neutropenia  Bernard-Soulier syndrome, with giant platelets and greater than expected bleeding for the degree of thrombocytopenia  Thrombocytopenia with absent radius (TAR) syndrome, with skeletal abnormalities  Gray platelet syndrome, with giant platelets lacking alpha granules and predisposition to myelofibrosis
  11. 11. Treatment  Major bleeding is rare in patients with ITP - platelet count <10,000  Goal for treatment is to provide a safe platelet count to prevent major bleeding rather than returning the platelet count to normal  Adults with severe thrombocytopenia (< 30,000) at the time of diagnosis are almost always treated even if they are asymptomatic or have only minor bleeding symptoms, course of the disease and future risk is unknown  Pts with severe chronic thrombocytopenia who have only partial response to treatment is uncertain – individual management decisions
  12. 12. Treatment  Glucocorticoids  The goal of initial glucocorticoid treatment is not to "cure" the ITP, but to support the platelet count in a safe range with minimal and tolerable side effects until a spontaneous remission occurs or until more definitive therapy established  Prednisone – standard practice – oral 1mg/kg single daily dose, most respond within 2 weeks, can taper once responds  High-dose dexamethasone – role of this is being actively investigated  Dosing of 40mg per day with PO or IV for 4-8 days  Follow response to treatment  IVIG: temporarily supports platelet count  Dose: 1g/kg/day for 1 or 2 days  Can use for life-threatening bleeding
  13. 13. References Immune thrombocytopenic purpura. NEJM 2002;346(13):995 Idiopathic thrombocytopenic purpura: a practice guideline developed by explicit methods for the American Society of Hematology. Blood 1996; 88:3 UTDOL