Hyperinsulinaemic hypoglycaemia (HH) occurs as a consequence of unregulated insulin secretion from pancreatic beta cells. It is the most common cause of severe and prolonged hypoglycemia in newborns. HH is a major risk factor for brain damage and subsequent neurological disability, which is why the identification, rapid diagnosis, and timely treatment of patients with HH are essential for the prevention of brain damage. The present case gives a brief description of a patient with congenital HH with an established mutation in the ABCC8 gene encoding the SUR1 subunit of the K-ATP channel. The genealogical tree, the clinical picture, the diagnostic cascade, the neurological consequences and their development in dynamics are considered, with special emphasis on the epileptic syndrome and mental status. Advances in molecular genetics, radiological imaging techniques, conservative treatment, or laparoscopic surgery may completely change the clinical approach to children with severe congenital forms of HH.

congenital hyperinsulinaemic hypoglycaemia, mental retardation, symptomatic epilepsy