The term lissencephaly comes from the Greek and is derived from "lissos" = smooth and "enkephalos" = brain and refers to the main abnormality, the smooth brain surface. Lissencephaly is based on a disturbance of neuronal migration and consequently of the normal six-layer structure of the mature cerebral cortex in humans. Agyria, pachygyria and subcortical band heterotopia (SBH) are also included under the umbrella term lissencephaly. There is both clinical and genetic overlap with other brain malformations, especially tubulinopathies.
The most common causes of lissencephaly are Miller-Dieker syndrome, which is caused by a contiguous gene syndrome due to microdeletion 17p13.3 or pathogenic variants in the PAFAH1B1 gene (formerly LIS1) located in this chromosomal region, as well as variants in DCX, the causative gene for X-linked lissencephaly or X-linked subcortical laminar heterotopy.
Di Donato et al. 2017, Am J Med Genet 173A:1473 / Fry et al. 2014, Am J Med Genet 166C:198