Immune thrombocytopenia (ITP): diagnosis including secondary ITP, and selection of second line treatment

This article summarizes our approach to the diagnosis, secondary ITP, and choice of second line options in patients with immune thrombocytopenic (ITP). We very briefly summarize first-line treatment and then utilize a case-based approach. We will first explore persistent-chronic ITP in a younger female. We consider many possibilities beyond primary ITP e.g., hypogammaglobulinemia, chronic infection, and anemia, and how to approach their diagnosis and management. The journey continues throughout pregnancy and post-partum and eventually includes fourth-line treatment after a late relapse. We then consider an older male, emphasizing differences in diagnostic considerations and management. The focus is on initiation and continuation of second line treatment, pros and cons of each option, and briefly the impact of treatment choices related to endemic presence of SARS-CoV-2. During review of potential second-line treatment options, we also briefly touch upon novel treatments. Finally, there is a short section on refractory disease drawn from our extensive review in Blood in February 2020(1). The clinical nature of the discussions replete with figures and tables and with interspersion of pearls regarding efficacy and toxicity at different ages and genders, will serve the reader in management of "typical" adult patients who develop persistent and chronic ITP.