Mild Encephalitis/Encephalopathy With a Reversible Splenial Lesion (MERS) in an Adult: An Associated Finding in Severe Acute Pancreatitis With Multisystem Involvement.

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is a rare clinico-radiological syndrome characterized by transient lesions of the splenium of the corpus callosum, typically occurring in the context of infections. While most frequently observed in children, adult cases remain infrequent and underreported. We present the case of a 30-year-old male patient with a preceding viral-like illness who was admitted for acute pancreatitis, renal failure, and neurological symptoms including confusion, dysarthria, ataxia, and postural tremors. An MRI of the brain revealed a reversible lesion in the splenium of the corpus callosum. Admission blood workup showed systemic inflammation, elevated inflammatory markers, and cytopenias, except cerebrospinal fluid (CSF) analysis and infectious serologies were unremarkable. The patient required hemodialysis and supportive management, including antibiotics, with clinical and radiological recovery of both the MERS and the other systems involved. This case highlights an atypical adult presentation of MERS associated with severe multisystem involvement, highlighting the importance of recognizing this syndrome in adults with systemic infectious syndromes and neurologic symptoms. Awareness of such presentations is essential for accurate diagnosis, timely intervention, and favorable outcomes.