Summary

A 26-year-old man presented to the emergency department with new-onset generalised tonic–clonic seizures. His clinical picture suggested either autoimmune or infectious encephalitis while his brain imaging raised the possibility of a stroke. A detailed developmental and childhood medical history added suspicion of a mitochondrial defect to the differential. After several molecular genetic analyses, an uncommon mitochondrial mutation was confirmed, unequivocally consistent with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome.