Idiopathic Thrombocytopenic Purpura (ITP)

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease

Pathophysiology

1) autoimmune condition marked by thrombocytopenia and purpuric rash 2) acute onse occurs typically in children after a viral exanthem or upper respiratory tract infection 3) in adults chronic onset is most typical 4) causes are formation of immune complexes containing virus particles that bind the Fc receptors on platelets with production of antibodies against viruses that cross-react with platelets

Signs and Symptoms

1) purpura (punctate hemorrhagic rash) 2) easy bruising 3) intracranial bleeding 4) heavy menstrual periods

Characteristic Test Findings

Laboratory – 1) thrombocytopenia (low platelet count) 2) mild anemia (low red blood cell count)

Inheritance/Epidemiology

1) female to male, 3:1, 2) chronic form most commonly affects women ages 20-40 years

Treatment

1) glucocorticoids (in mild cases) 2) intravenous immunoglobulins 3) anti-RhD (WinRho) 4) specific antibody preparations 5) splenectomy (removal of spleen) in steroid-resistant or dependent cases 6) as a last resort immunosuppressive drugs can be used (azathioprine, cyclophosphamide, vincristine, cyclosporine)

Tips for USMLE

1) conditions other than ITP that can present with thrombocytopenia (low platelet count) – lupus, lymphoma, leukemia, and HIV 2) if a 6 year old girl appears to be recovering from “fifth’s disease,” but then develops a purplish rash on her torso and a platelet count of 18,000 think ITP