Congenital malformations are physical defects detectable in an infant at birth which can involve many different parts of the body, including the brain, heart, lungs, liver, bones, or intestinal tract.

The disorder arises from the deletion of part of the small arm of chromosome 17p (which includes both the LIS1 and 14-3-3 epsilon genes), leading to partial monosomy.

The face, especially in children, has distinct characteristics including a short nose with upturned nares, thickened upper lip with a thin vermilion upper border, frontal bossing, small jaw, low-set posteriorly rotated ears, sunken appearance in the middle of the face, and hypertelorism of eyes.

In less than 20% of cases an unaffected parent carries a particular chromosomal rearrangement called a balanced translocation, in which no genetic material is gained or lost.

[citation needed] The disease may be diagnosed by cytogenetic techniques like fluorescence in situ hybridization (FISH), testing for a microdeletion at LIS1.

MRI facilitates early detection of this syndrome in children by revealing a "smooth brain" image, also called lissencephaly.

FDNA provides a service that in turn increases the chances of detecting these distinct characteristics, which, when shown to a geneticist, can assist in reaching the right medical diagnosis.

Couples who are considering prenatal diagnosis are usually advised to discuss the risks and benefits of this type of testing with a geneticist or genetic counselor.

[citation needed] While no cure for MDS is available yet, many complications associated with this condition can be treated, and a great deal can be done to support or compensate for functional disabilities.

Because of the diversity of the symptoms, it can be necessary to see a number of different specialists and undergo various examinations, including:[citation needed] This disease is fairly uncommon, and treatment is scarce.

Some children may be able to sit up, crawl, or say a few basic words, but most are severely developmentally delayed and remain at the level of infants for their lifetime.

The hallmark of MDS is lissencephaly, a condition in which the outer layer of the brain, the cerebral cortex, is abnormally thick and lacks the normal convolutions (gyri).

[citation needed] JQ Miller described the disease and in 1969 H Dieker emphasized that it should also take the name lissencephaly syndrome because several malformations occur beyond the brain itself.