Abstract
Lobar holoprosencephaly (HPE) represents the mildest form of HPE, featuring an interhemispheric fissure extending along most of the entire midline, with the thalami remaining unfused. Lobar HPE is usually diagnosed in the prenatal stage or infancy; however, cases of adult-onset are exceedingly rare. Here, we present a 25-year-old patient who was presented with multiple episodes of seizures and was subsequently diagnosed with lobar HPE accompanied by a meningocele. By shedding light on this rare brain malformation, we hope to raise awareness among healthcare professionals and stimulate further research into the pathogenesis, clinical course, and management of adult-onset HPE.