Renal failure and posterior reversible encephalopathy syndrome in patients with thrombotic thrombocytopenic purpura

Background: Little is known of the nature of the neurologic manifestations in thrombotic thrombocytopenic purpura (TTP). We have recently reported posterior reversible encephalopathy syndrome (PRES) as the predominant brain abnormality in patients with TTP. Posterior reversible encephalopathy syndrome has been associated with a variety of medications and pathologic states including increased arterial blood pressure and renal failure. The factors that predispose patients with TTP to PRES are not known. Objectives: To ascertain whether the presence and degree of hypertension and typical laboratory abnormalities seen in hospitalized patients with TTP are predictors of PRES. Design, Setting, and Patients: We performed a retrospective analysis of brain imaging in 46 hospitalized patients with acute TTP seen at St Mary's and Rochester Methodist hospitals in Rochester, Minnesota, from January 1997 to June 2007. Head computed tomographic scans and brain magnetic resonance images were evaluated independently by 2 investigators. We then performed statistical analysis to determine whether the presence of PRES was associated with the presence of hypertension or abnormal laboratory data, including renal function. Results: Forty-seven incidences of patients having TTP and neuroimaging were evaluated over a 10-year period. Thirty-three patients (70%) had brain magnetic resonance imaging performed. Of the patients who had acute abnormalities on brain magnetic resonance imaging, 13 (48%) were found to have PRES. Degree of hypertension was not associated with PRES on brain magnetic resonance imaging (P=.55). There was no association between hematocrit or platelet nadir, maximum blood urea nitrogen, D dimer, fibrinogen, lactate dehydrogenase, or total bilirubin levels and occurrence of PRES. The only variable highly associated with PRES on neuroimaging was the glomerular filtration rate (P=.02). Conclusion: The occurrence of PRES in patients with acute TTP is associated with worse renal function.