Lissencephaly is a brain abnormality caused by a defect in the way neurons move during the development of the brain. The human cortex normally has many folds, which are called sulci and gyri. Individuals with lissencephaly have an absence or reduction in this folding. An absence of folding is known as agyria, and where the folds are less numerous and thicker the term pachygyria is used. Those individuals who suffer with lissencephaly, present with a range of symptoms including learning difficulties and epileptic seizures.
It is a rare disease with an incidence of approximately 1 in 100,000 births. Lissencephaly can be caused by infection during pregnancy, however in most instances is caused by genetic mutations. These mutations can be inherited or can occur spontaneously during pregnancy. Mutations in the following genes are known to cause lissencephaly: LIS1, DCX; Reelin; ARX; and TUBA1A.