This is a longitudinal observational study that seeks to evaluate for the prevalence and extent of cognitive dysfunction in adults with persistent and chronic ITP. Following enrollment, subjects will complete neurocognitive testing using the NIH Toolbox Cognition Battery (NIHTB-CB). In addition, subjects will complete surveys for patient-reported outcomes of quality of life, fatigue, self-reported cognitive function, and depression. Background characteristics and relevant clinical history will be obtained through an enrollment survey and chart review. The primary aim of the study is to describe the prevalence and extent of cognitive impairment in ITP and explore associated risk factors. This study will also assess the feasibility of longitudinal cognitive testing in patients with ITP and describe any observed changes in cognition over time.