Distal 18q- Basics

Receiving a diagnosis of distal 18q- can be a very difficult and confusing experience for families. Although it may explain why a child has medical problems or developmental delays, it also brings a lot of new questions. The good news is that we know a lot about distal 18q-, and we are continuing to learn more through the ongoing research at the Chromosome 18 Clinical Research Center.

On this page, we are going to answer the most common questions parents have when their child is first diagnosed with distal 18q-. More detailed information is available and can be found by clicking the links within the text on this page.

We also encourage you to speak with a genetics provider in your area to learn more about what this diagnosis means for you and your family.

Distal 18q- happens when a piece of the long arm of one of the two copies of chromosome 18 is missing. This means there is one copy instead of two for each of the genes in the deleted region of the chromosome. This condition is different from another condition called proximal 18q-. Distal 18q- is caused by a deletion that is closer to the end of the chromosome and often includes the tip of the chromosome.

Distal 18q- occurs when a piece of chromosome 18 is lost. This change likely occurred in the egg or sperm prior to conception or very shortly after conception. There is no known cause of distal 18q-.

Distal 18q- is usually diagnosed when an infant or child has health and/or developmental concerns. Most often, the diagnosis is made by a blood test. This test looks at the chromosomes to see whether a piece of chromosome is missing.

Some babies with distal 18q- may have health problems that are noticeable at birth. For example, they may have a heart or a foot defect. They may have a hole in the roof of their mouth, known as a cleft palate. They may have breathing or feeding difficulties during the neonatal period. Other health problems frequently develop as babies with distal 18q- get older. In particular, people with distal 18q- have a higher likelihood of having hormone abnormalities, seizures, kidney problems, and changes in their immune system. They often have hearing and vision problems. There are other health problems that have been reported in people with distal 18q-, but these are the most common.

There is a great deal of variability among people with distal 18q-. At this point in time, it is impossible to predict exactly how it will affect a person. However, knowing about this diagnosis helps families and their health care team know what to look out for.

Most children with distal 18q- have developmental delays. This means that they do not meet their milestones on time, but they do achieve them. For example, they may roll over, walk, and talk later than other children. Almost all people with distal 18q- will have some intellectual or learning disability. This means they will have more difficulty learning and developing new skills. The degree of intellectual disability varies greatly. If the deletion includes a certain gene (TCF4), the intellectual disability is usually more significant.

Pitt Hopkins syndrome is a condition that is caused by a small change impacting one gene on the long arm of chromosome 18: TCF4. Some people with distal 18q- have deletions that include TCF4. These individuals often have features of Pitt Hopkins syndrome, including changes in breathing patterns, a higher likelihood of seizures, and lack of speech, and more significant intellectual disability. For more information about Pitt Hopkins syndrome, visit the Pitt Hopkins Research Foundation.

There are about 100 genes in the area affected by distal 18q-. They play various roles in a person’s growth, development, and overall health. Currently, research is focused on understanding how missing specific genes on chromosome 18 lead to health and developmental concerns. We know that many of the genes on 18 do not cause problems when one copy is missing. However, there are a handful of genes that we think may be associated with specific features.

It is difficult to predict how an individual will be affected by a deletion of distal 18q. However, we know that children with distal 18q- go to school, develop new skills, make friends, and are active members of their communities.

Every child with distal 18q- is different. However, we can make some recommendations for evaluations to ensure that the most common concerns are identified and addressed early. The Chromosome 18 Clinical Research Center has created a “Distal 18q- Management Guide”. We strongly recommend reviewing this document for additional details and information about managing distal 18q-. Some of the management recommendations include the following:

Depending on a person’s health concerns, additional screenings or management strategies may be necessary. It is important to discuss a health care plan with your team of healthcare providers.

The Chromosome 18 Clinical Research Center is dedicated to fully understanding the chromosome 18 conditions as well as to developing treatments for these conditions. For additional information or to enroll in the study, please visit their website.

The Chromosome 18 Registry & Research Society is dedicated to making chromosome 18 conditions the first treatable chromosome abnormalities. We count within our membership thousands of parents, siblings, extended family and friends, businesses, and affected individuals. Registry membership is open to any interested person.

We invest in both people and science; supporting our members through education and a sense of community while also focusing squarely on impactful clinical research that will lead to healthier, happier, and more independent lives for those affected and their families.

There is a great deal of additional information on our website, as well as the opportunity to connect with other parents. To become a member, please go to our home page and click the “become a member” button.