Miller-Dieker syndrome is microdeletion syndrome due to hemizygote deletion of region 17p13.3 where are located more than 50 genes. Phenotype is clinically characterized by severe hypotonia, facial dysmorphy with high nasal bridge, prominent upper lip over micrognathia, bitemporal narrowing, dysplastic, low set and posteriorly angulated auricles. Epileptic seazures, progressive spasticity with opisthotonus, failure to thrive, growth and developmental retardation, cardial and renal anomalies lead to early death before age of 3 years. By autopsy is found lissencephaly with massive neuronal heterotopies and large ventricular cavities of embryonic type, pachygyria and a figure-eight appearence of brain due to wide opened Silvian fossa. Histologically is comfirmed incomplet development of brain like fetal architecture of 3 - 4 months gestation with heterotopias and a thickened cortex with 4 rather than 6 layers. Article refers a case of 3-months old boy with Miller-Dicker syndrome due to new mutation in chromosomal structure.

        Key words: Miller-Dieker syndrome, microdeletion 17p13.3, lissencephaly, severe hypotonia, seazures, progressive spasticity, facial dysmorphy, failure to thrive, early death, etiology in new or inherited mutation