Down syndrome occurs when a child is born with extra genetic material from chromosome 21. This can mean they have either a full or partial extra copy. The disease, which affects roughly one in 700 babies in the United States each year, is associated with weak muscle tone and delays in cognitive development. It is also typically characterized by eyes that slant upward and short stature.
Types of Down Syndrome
According to the National Down Syndrome Society (NDSS), three different types of Down syndrome exist.
Trisomy 21 occurs when someone is born with three copies of chromosome 21. The body normally has two copies. Roughly 95 percent of people with Down syndrome have trisomy 21.
Mosaicism is also characterized by having three copies of chromosome 21. But unlike Trisomy 21, this additional genetic material is only present in some of the initial cell divisions after fertilization. What this means is that some of the cells contain the normal amount of chromosomes, while others contain an extra one. Mosaicism is a rare occurrence.
Translocation is another rarer form of Down syndrome where part of chromosome 21 separates itself out during cell division, and then attaches to another chromosome.
Risk Factors and Treatment
When it comes to Down syndrome, a variety of risk factors come into play. The biggest one is maternal age. Mothers over the age of 35 are at greater risk for having a child with the condition. According to the NDSS, a 28-year-old woman has about a one in 1,000 chance of having a child with Down syndrome. However, a 35-year-old woman’s chances are one in 350. The odds only increase as the mother gets older. At this point, heredity is not commonly associated with Down syndrome. But if a woman already has a child with trisomy 21, she has about a one in 100 chance of having another baby with the same condition. Many interventions are available to children with Down syndrome.
According to the National Institute of Child Health and Human Development, early intervention and developmental support can be provided to children as young as a few months old. Upon entering the school system, special education services will also be provided by the school district. This may include speech and language therapy, occupational therapy and physical therapy.
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