<prompt> Answer this question truthfullyWhat is the pentad of classical symptoms seen in thrombotic thrombocytopenic purpura TTP, and how can it be remembered using the mnemonic FAT RN?  <response>: <reason> The pentad of classical symptoms seen in thrombotic thrombocytopenic purpura TTP includes Fever 15 patients, Anemia Microangiopathic Hemolytic Anemia, Thrombocytopenia, Renal symptoms 12 of patients-More common in HUS, and Neurologic symptoms 23 of patients-More common in TTP. This pentad can be remembered using the mnemonic FAT RN, where F stands for Fever, A stands for Anemia Microangiopathic Hemolytic Anemia, T stands for Thrombocytopenia, R stands for Renal symptoms 12 of patients-More common in HUS, and N stands for Neurologic symptoms 23 of patients-More common in TTP. 