We describe the clinical, electroencephalography (EEG), and developmental features of a patient with developmental and epileptic encephalopathy due to a homozygous pathogenic variation of mitochondrial glutamate/H⁺ symporter SLC25A22. Epilepsy began during the first week of life with focal onset seizures. Interictal EEG revealed a suppression-burst pattern with extensive periods of non-activity. The prospective follow-up confirmed developmental encephalopathy as well as ongoing active epilepsy and almost no sign of development at 8 years of age. We confirm in the following paper that SLC25A22 recessive variations may cause a severe developmental and epileptic encephalopathy characterized by a suppression-burst pattern. On the basis of an in-depth literature review, we also provide an overview of this rare genetic cause of neonatal onset epilepsy.