Case 27.1 reports a male who, at the age of 5 years, lost consciousness and presented with right-sided hemiparesis. A second episode occurred at 7 years of age: during a respiratory infection complicated with pneumonia, he transiently lost consciousness and vision. Afterward, he had moderate, non-migrainous, and infrequent headaches. At the age of 10 years, after an unspecified illness, focal convulsive status epilepticus (epilepsia partialis continua) occurred with deviation of head and eyes to the right and twitching of the right side of the face, accompanied by left-sided focal spike and slow-wave activity. The status was refractory to all intravenous antibiotics. The boy died within 10 h due to recurrent status epilepticus, acidosis, anuria, and respiratory failure. Genetic analysis revealed that the patient had Alpers- and mitochondrial neurogastointestinal encephalomyopathy (MNGIE)-like disease with disturbed cerebrospinal fluid (CSF) folate transport and an unusual mode of genetic transmission of the POLG mutation. Case 27.2 reports a nine-year-old male patient who developed bilateral sensorineural hearing loss followed by a generalized tonic–clonic seizure. From this period, he had monthly headaches without other signs, usually of moderate severity. From age 15, he had multiple episodes of stroke, leading to multi-organ failure and death at the age of 16 years. Genetic mutation- heteroplasmic m.3764C > G variant in MT-ND1.