Despite the undoubted progress of medical science around the world, recently, there has been a tendency of an increase in the frequency of congenital malformations and hereditary diseases in children. Therefore, the knowledge of the symptoms of various hereditary syndromes in children determine the diagnosis and tactics of further therapy, which is of great importance not only for the prognosis of the disease, but also the quality of the patient's future life. The article presents a clinical case of Proteus syndrome (PS) in a young child against the background of congenital malformation of the brain (left hemimegalencephaly). According to the results of ultrasound screening in the second half of pregnancy, there were revealed multiple congenital malformations of the сentral nervous system in the fetus of the mother of the child. After birth, the patient was observed in the Department of pathology of newborns, where he was first diagnosed with Proteus syndrome against the background of congenital abnormalities of the brain. From 2 months of age, the child had attacks in the form of infantile spasms. And at the age of 6 months, some changes of epileptiform character were identified on EEG. The child was constantly receiving anticonvulsant therapy. At the age of 8 months, in the Acad. N. N. Burdenko Research Institute of Neurosurgery he underwent surgery – anatomic left hemispherectomy. After surgical treatment, the patient was discharged in a satisfactory condition with the main clinical diagnosis: congenital malformation of the brain (left hemimegalencephaly), symptomatic focal left hemisphere pharmacoresistant epilepsy. Convulsions did not occur during anticonvulsant therapy. In 1 year and 2 months the patient was examined and consulted by a geneticist at the Medical and Genetic Research Center in Moscow, where it was concluded: given the results of genomic sequencing, most likely, the child has Proteus-like syndrome. Medium congenital melanocytic nevus. The patient is disabled with a gross delay in neuro-psychical development. It is planned to remove the formation of the left cheek with the obligatory histological examination.