MEHMO syndrome (OMIM: 300148; ORPHA: 85282) is a disease appears by mental retardation, epilepsy seizures, hypogonadism, microcephaly, and obesity. Pathology is associated with mutations in the EIF2S3 gene located on the X chromosome and leads usually to serious disability of patients. The article presents a clinical observation of the case of the syndrome in two male cousins with microcephaly, manifested by a complex of endocrinopathies (hyperinsulinemic hypoglycemia, multiple adenohypophysis hormone deficiency) and accompanied by severe neurological abnormalities (epilepsy, spastic tetraparesis, optic nerve atrophy). The complexity of the diagnostic due to the rarity of this syndrome, is described.