Proximal 18q deletion syndrome - Chromosome 18

Proximal 18q deletion syndrome is a chromosomal disorder due to the absence of a part of the long arm of chromosome 18. The term "proximal" means that the missing part occurs near the center of the chromosome.

This condition can lead to a wide variety of signs and symptoms. Most people with proximal 18q deletion syndrome manifest a delay in the development of skills such as sitting, crawling, walking and talking, and intellectual disabilities that can vary from mild to severe. In particular, these individuals may manifest a delay in the ability of expressive language. In addition, these people frequently suffer episodes of epilepsy, hypotonia, and behavioral problems, such as hyperactivity, aggressiveness, hyperphagia and autism spectrum disorders. Some affected people have macrocephaly, and it is common for them to have certain facial features such as a prominent forehead, ptosis or drooping of the eyelid, palpebral fissures tilted down and bulging periorbital tissue.

Proximal 18q deletion syndrome is due to a deletion of genetic material from a copy of chromosome 18. The deletion occurs near the center of the long arm of the chromosome, usually in an area between regions 18q11.2 and 18q21.2. The size of the deletion varies among affected individuals.

It is believed that the signs and symptoms of this syndrome are related to the loss of multiple genes from this part of chromosome 18. This process is considered to have an autosomal dominant inheritance pattern, which means that a copy of the region removed on chromosome 18 in each cell is sufficient to cause disease characteristics. Most cases are due to a new deletion and are not inherited. Deletion frequently occurs as a random event during the formation of reproductive cells or at the beginning of embryonic development, so that affected people generally have no history of the disease in their family.

Tests performed in IVAMI: in IVAMI we perform the detection of mutations associated with proximal 18q deletion syndrome, by means of the PCR quantification at real time.

Recommended samples non-coagulated blood obtained with EDTA for separation of blood leukocytes, or a card with a dried blood sample (IVAMI can mail the card to deposit the blood sample).