Idiopathic Posterior Reversible Encephalopathy Syndrome (PRES) in a 4-month-old infant: a case report

BACKGROUND: Posterior Reversible Encephalopathy Syndrome (PRES) is a clinico-radiological condition characterized by acute neurological symptoms associated with vasogenic cerebral edema. Although increasingly recognized in pediatric populations, PRES remains exceptionally rare in infants younger than six months, making diagnosis particularly challenging in this age group. CASE PRESENTATION: We report the case of a 4-month-old previously healthy infant admitted for recurrent afebrile generalized tonic-clonic seizures. Initial clinical examination, laboratory investigations, cerebrospinal fluid analysis, and cranial computed tomography were unremarkable. Brain magnetic resonance imaging revealed bilateral, symmetrical cortico-subcortical occipital hyperintensities on T2-weighted and FLAIR sequences, with diffusion-weighted hyperintensity and mildly reduced ADC signal, overall suggestive of PRES with a possible superimposed cytotoxic component. No sustained arterial hypertension or underlying metabolic, infectious, autoimmune, or toxic cause was identified despite extensive evaluation, supporting the diagnosis of idiopathic PRES. Seizures were controlled with antiepileptic therapy, and the clinical course was favorable without early recurrence. CONCLUSION: This case highlights an exceptionally early presentation of idiopathic PRES in infancy and underscores the need to consider this diagnosis in unexplained seizures, even in the absence of classical risk factors. Early MRI is essential for diagnosis, and long-term neurodevelopmental follow-up remains crucial given the uncertain prognosis in this age group.