Mild encephalitis/encephalopathy with a reversible splenial lesion: a rare manifestation of Mycoplasma pneumoniae infection in adults.

Mild encephalitis/encephalopathy with a reversible splenial lesion is a rare clinico-radiological syndrome in adults. It typically presents with altered consciousness, headache, or seizures, often preceded by a febrile prodrome. Brain magnetic resonance imaging (MRI) usually shows a transient lesion in the central portion of the splenium of the corpus callosum. We describe the case of a 23-year-old man who developed headache, confusion, and nausea after a brief febrile episode without respiratory symptoms. His neurological examination was unremarkable. Brain MRI demonstrated a small diffusion-restricted hyperintensity in the splenium of the corpus callosum. Serologic testing was positive for Mycoplasma pneumoniae. Chest CT was normal. He was treated with azithromycin and achieved complete clinical and radiological recovery. This case highlights the importance of recognizing this rare entity in adults, particularly as an uncommon neurological manifestation of Mycoplasma pneumoniae, even in the absence of pulmonary involvement.