This is a phase two, single-arm, open-label study through Peking University People’s Hospital in China to study the efficacy and safety of acetylcysteine (also called N-acetylcysteine or NAC) and high dose dexamethasone for therapy in adults with newly diagnosed ITP. NAC is a therapy that has traditionally been used to treat cystic fibrosis and other respiratory conditions by reducing mucous secretions. Recently, it’s been studied in patients with other platelet disorders such as thrombotic thrombocytopenic purpura (TTP) and is now being investigated for its potential treatment of ITP. In this study, NAC would be given orally, three times a day, in combination with a four-day high-dose pulse treatment of dexamethasone. Eligibility is restricted to adult patients with newly diagnosed ITP who have never had cancer or a splenectomy, are between the ages of 18-80 years, and have not been treated previously with Rituxan®. Participants must also have a diagnosis of primary ITP and have a platelet count under 30,000μL.