What is mosaic Down syndrome?

Mosaic Down syndrome is a rare form of Down syndrome where a percentage of cells have a third copy of the 21st Chromosome and the remaining cells are unaffected.

According to research, approximately 150 babies are born each year in America with mosaic Down syndrome. Although it is believed advanced maternal age increases the risk of having a child with mosaic Down syndrome, mothers of all ages have children with this disorder and the majority of the maternal age is between 20 and 30 years old. Individuals with mosaic Down syndrome can be diagnosed before or at birth or as late as adulthood. The main reason for late diagnoses is due to the lack of physical characteristics present in an individual with Down syndrome and the lack of knowledge of this rare disorder.

Medical Conditions

There are a variety of medical conditions that are possible in a person with Down syndrome. Because an individual with mosaic Down syndrome has a percentage of Down syndrome cells, the risk of having these medical conditions are probable. It is important that the patient’s physician follow the Health Care Guidelines for Children with Down syndrome.

Lower resistance to infection
Respiratory infections
Vision problems
Frequent ear infections
Mild to moderate hearing loss
Congenital Heart Defects
Gastrointestinal track problems
Atlantoaxial Instability
Thyroid Dysfunction
Sleep Apnea
Alzheimer disease
Increased risk of Leukemia
Celiac Disease
Obesity

Developmental Delays

Children with mosaic Down syndrome may experience developmental delays in speech, fine motor and gross motor development. Research has shown that the majority of babies with mosaic Down syndrome develop at a slightly faster rate than those with Down syndrome. Most areas of the world offer Early Intervention services to assist children with developmental delays. Some delays that may be present are:

Low muscle tone
Speech delays
Sucking and Feeding
Rolling over
Sitting up
Crawling
Walking
Climbing
Pincher grasp

Special Education

Children with mosaic Down syndrome have a wide variety of abilities. Some may take longer to learn certain concepts, such as math, than their peers. Most countries have laws in place to allow children with special needs to attend regular education classrooms with modifications available if needed. Early Intervention usually ends at the age of 3 yr. old, so the child will then be placed in a special preschool program to continue services such as Speech Therapy, Occupational Therapy, or Physical Therapy. Parents have many options on where and how they wish their child to be placed. It is important for parents to find out all options before they make a decision on the best placement for their child.

Current research is being conducted to discover the differences of IQ levels in those with mosaic Down syndrome compared to those with Down syndrome. Most individuals with mosaic Down syndrome are reported to have some level of mental disability. Math and number concepts seem to be the most prevalent problem individuals with mosaic Down syndrome face. With proper guidance, individuals can succeed to the best of their ability.

Adolescence with mosaic Down syndrome

Adolescence with mosaic Down syndrome have the same feelings as those without mosaic Down syndrome. They wish to date, have friends, and do all the things that their peers do. It is important to find activities that the adolescent can be involved in to increase social skills and help self-esteem.

Adolescence with mosaic Down syndrome do experience hormonal changes during adolescence. Therefore, teenagers with mosaic Down syndrome should be educated about their sexual drives.

Research has shown that males with Down syndrome typically have a reduced sperm count and therefore, in most cases, can not father children. However, there has been no research on males with mosaic Down syndrome concerning this issue. Down syndrome research shows that women do have menstrual periods and are able to become pregnant and carry their baby to term. This holds true for women with mosaic Down syndrome.

Adults with mosaic Down syndrome

Adults with mosaic Down syndrome can lead productive lives. Many live on their own, hold jobs, marry, and have children. The outcome of their children having mosaic Down syndrome or Down syndrome depends on where the extra chromosomes are located in their body. If the extra chromosomes are not located in reproductive areas, it is more likely that their offspring will not have extra chromosomes.

The life span of a person with mosaic Down syndrome has increased dramatically due to the medical advances in the last few decades. It is reported that people with Down syndrome can live to the age of 50 and above. Reports have shown that individuals with mosaic Down syndrome have lived into their 80’s.

Some information in this document was provided by:
Down syndrome Quarterly
Dr. Leshin Ds Health
National Dissemination Center for Children with Disabilities
Virginia Commonwealth University/Medical College of Virginia