Can You Have an Extra Chromosome and Be Normal

Down's syndrome is a status in which a person has an extra chromosome.

What is Down syndrome?

Down's syndrome is a condition in which a person has an extra chromosome. Chromosomes are small "packages" of genes in the body. They decide how a baby's body forms and functions as it grows during pregnancy and after nascence. Typically, a baby is built-in with 46 chromosomes. Babies with Down syndrome accept an extra copy of 1 of these chromosomes, chromosome 21. A medical term for having an extra copy of a chromosome is 'trisomy.' Down's syndrome is also referred to as Trisomy 21. This extra re-create changes how the baby's body and brain develop, which can crusade both mental and physical challenges for the baby.

Even though people with Downwards syndrome might act and look similar, each person has different abilities. People with Down's syndrome usually have an IQ (a measure out of intelligence) in the mildly-to-moderately low range and are slower to speak than other children.

Some common physical features of Down's syndrome include:

• A flattened face, particularly the bridge of the olfactory organ
• Almond-shaped eyes that camber up
• A curt neck
• Small ears
• A tongue that tends to stick out of the rima oris
• Tiny white spots on the iris (colored part) of the centre
• Modest hands and feet
• A single line beyond the palm of the hand (palmar pucker)
• Minor pinky fingers that sometimes bend toward the thumb
• Poor muscle tone or loose joints
• Shorter in height equally children and adults

How Many Babies are Built-in with Down Syndrome?

Down syndrome remains the about mutual chromosomal status diagnosed in the United States. Each twelvemonth, virtually 6,000 babies born in the United States have Downwards syndrome. This means that Down syndrome occurs in about one in every 700 babies.¹

Types of Down Syndrome

There are three types of Down syndrome. People oftentimes tin can't tell the difference between each type without looking at the chromosomes because the physical features and behaviors are similar.

• Trisomy 21: Almost 95% of people with Down syndrome have Trisomy 21.² With this type of Down's syndrome, each cell in the body has three divide copies of chromosome 21 instead of the usual two copies.
• Translocation Down syndrome: This type accounts for a pocket-sized percent of people with Down's syndrome (virtually 3%).² This occurs when an extra function or a whole extra chromosome 21 is present, but it is attached or "trans-located" to a different chromosome rather than being a separate chromosome 21.
• Mosaic Downwardly syndrome: This type affects nearly 2% of the people with Down's syndrome.² Mosaic ways mixture or combination. For children with mosaic Down's syndrome, some of their cells have 3 copies of chromosome 21, merely other cells have the typical two copies of chromosome 21. Children with mosaic Downward syndrome may have the same features every bit other children with Down syndrome. However, they may have fewer features of the condition due to the presence of some (or many) cells with a typical number of chromosomes.

Causes and Risk Factors

• The actress chromosome 21 leads to the concrete features and developmental challenges that tin occur amidst people with Down syndrome. Researchers know that Down syndrome is caused by an extra chromosome, simply no one knows for sure why Down's syndrome occurs or how many different factors play a role.
• One cistron that increases the chance for having a baby with Down syndrome is the mother'southward age. Women who are 35 years or older when they become pregnant are more than probable to take a pregnancy affected past Downwardly syndrome than women who become meaning at a younger historic period.^3-5However, the majority of babies with Down syndrome are built-in to mothers less than 35 years old, because there are many more births among younger women.^6,7

Diagnosis

In that location are ii basic types of tests available to detect Down syndrome during pregnancy: screening tests and diagnostic tests. A screening examination tin can tell a woman and her healthcare provider whether her pregnancy has a lower or higher gamble of having Downwardly syndrome. Screening tests do not provide an absolute diagnosis, but they are safer for the mother and the developing baby. Diagnostic tests can typically notice whether or not a babe will have Down's syndrome, merely they tin can be more risky for the mother and developing infant. Neither screening nor diagnostic tests can predict the full impact of Down's syndrome on a baby; no one tin can predict this.

Screening Tests

Screening tests oft include a combination of a claret examination, which measures the amount of various substances in the mother's claret (due east.g., MS-AFP, Triple Screen, Quad-screen), and an ultrasound, which creates a picture of the babe. During an ultrasound, one of the things the technician looks at is the fluid behind the infant'south neck. Extra fluid in this region could bespeak a genetic problem. These screening tests can assist make up one's mind the baby's risk of Down syndrome. Rarely, screening tests can requite an aberrant result fifty-fifty when there is zip wrong with the baby. Sometimes, the test results are normal and yet they miss a problem that does exist.

Diagnostic Tests

Diagnostic tests are ordinarily performed after a positive screening test in guild to confirm a Downwardly syndrome diagnosis. Types of diagnostic tests include:

• Chorionic villus sampling (CVS)—examines material from the placenta
• Amniocentesis—examines the amniotic fluid (the fluid from the sac surrounding the babe)
• Percutaneous umbilical blood sampling (PUBS)—examines blood from the umbilical cord

These tests wait for changes in the chromosomes that would signal a Down's syndrome diagnosis.

Other Wellness Problems

Many people with Down syndrome have the common facial features and no other major birth defects. Nevertheless, some people with Down syndrome might have ane or more major birth defects or other medical issues. Some of the more than common wellness problems amidst children with Down syndrome are listed below.⁸

• Hearing loss
• Obstructive sleep apnea, which is a status where the person'southward animate temporarily stops while comatose
• Ear infections
• Eye diseases
• Heart defects present at birth

Wellness care providers routinely monitor children with Downwards syndrome for these weather.

Treatments

Down syndrome is a lifelong condition. Services early in life will often help babies and children with Down syndrome to improve their physical and intellectual abilities. Most of these services focus on helping children with Down syndrome develop to their full potential. These services include spoken language, occupational, and physical therapy, and they are typically offered through early intervention programs in each state. Children with Down syndrome may as well demand actress help or attention in school, although many children are included in regular classes.

Other Resources

The views of these organizations are their ain and do non reflect the official position of CDC.

• Down Syndrome Research Foundation (DSRF)external icon
  DSRF initiates research studies to better understand the learning styles of those with Downwards syndrome.
• Global Down syndrome Foundationexternal icon
  This foundation is dedicated to significantly improving the lives of people with Down's syndrome through research, medical care, education and advancement.
• National Association for Down's syndromeexternal icon
  The National Clan for Down syndrome supports all persons with Down syndrome in achieving their full potential. They seek to assist families, brainwash the public, address social bug and challenges, and facilitate active participation.
• National Downwardly Syndrome Society (NDSS)external icon
  NDSS seeks to increase awareness and acceptance of those with Down's syndrome.

References

1. Mai CT, Isenburg JL, Canfield MA, Meyer RE, Correa A, Alverson CJ, Lupo PJ, Riehle‐Colarusso T, Cho SJ, Aggarwal D, Kirby RS. National population‐based estimates for major birth defects, 2010–2014. Nascence Defects Enquiry. 2019; 111(18): 1420-1435.
2. Shin M, Siffel C, Correa A. Survival of children with mosaic Downward syndrome. Am J Med Genet A. 2010;152A:800-1.
3. Allen EG, Freeman SB, Druschel C, et al. Maternal historic period and adventure for trisomy 21 assessed by the origin of chromosome nondisjunction: a report from the Atlanta and National Down's syndrome Projects. Hum Genet. 2009 Feb;125(1):41-52.
4. Ghosh South, Feingold E, Dey SK. Etiology of Down's syndrome: Evidence for consequent clan among contradistinct meiotic recombination, nondisjunction, and maternal historic period across populations. Am J Med Genet A. 2009 Jul;149A(7):1415-20.
5. Sherman SL, Allen EG, Bean LH, Freeman SB. Epidemiology of Down's syndrome. Ment Retard Dev Disabil Res Rev. 2007;13(3):221-vii.
6. Adams MM, Erickson JD, Layde PM, Oakley GP. Downwards's syndrome. Recent trends in the U.s.. JAMA. 1981 Aug 14;246(seven):758-threescore.
7. Olsen CL, Cross PK, Gensburg LJ, Hughes JP. The furnishings of prenatal diagnosis, population ageing, and changing fertility rates on the live nascency prevalence of Down syndrome in New York State, 1983-1992. Prenat Diagn. 1996 Nov;xvi(xi):991-1002.
8. Balderdash MJ, the Committee on Genetics. Health supervision for children with Down's syndrome. Pediatrics. 2011;128:393-406.

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Source: https://www.cdc.gov/ncbddd/birthdefects/downsyndrome.html

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