Normotensive Posterior Reversible Encephalopathy Syndrome of an Unknown Etiology.

Posterior reversible encephalopathy syndrome (PRES) is a neurological disorder commonly associated with hypertension, preeclampsia, eclampsia, and renal dysfunction. However, normotensive presentations without an identifiable etiology remain rare, particularly in pregnancy. We report the case of a 25-year-old primigravida at 22 weeks of gestation who presented with new-onset generalized tonic-clonic seizures, altered sensorium, and bilateral papilledema. Despite the absence of hypertension or predisposing obstetric complications, MRI findings revealed characteristic vasogenic edema in the bilateral parieto-occipital lobes, supporting a diagnosis of PRES. Extensive investigations, including infectious, autoimmune, and thrombotic workups, failed to identify an underlying etiology. The patient's condition deteriorated, ultimately resulting in mortality. This case highlights an atypical, normotensive presentation of PRES in pregnancy without the common precipitating factors. While PRES is classically considered a reversible condition, this case underscores the potential for poor outcomes in the absence of timely intervention. Additionally, it raises the question of whether encephalitis or encephalopathy may act as potential triggers for PRES in patients without traditional risk factors.