Jacob, a child with Down Syndrome, enjoying a family holiday and browsing in shops, like any other 5 year old child wouldJacob looking at books and watching TV at age 6 years - Down Syndrome doesn't stop normal development, but social attitudes do. - Jacob, a baby with Down Syndrome - Jacob at one year of age

Comprehensive Down Syndrome Glossary, Word Dictionary and Definitions

This Comprehensive Down Syndrome Glossary, Word Dictionary and Definitions is Arranged in Alphabetical Order

AFB/free beta test – a set of two laboratory blood tests for alpha feto protein and beta human chorionic gonadotropin, both produced by the developing child or the placenta. This test is generally performed between 13 and 22 weeks of pregnancy, and offers a detection rate of 80% with a false positive rate of 2.8%.

alpha feto protein – a plasma protein that is normally produced by the developing fetus. Abnormally low levels can serve as an early indication of Down’s Syndrome

amniocentesis – medical laboratory test used in prenatal diagnosis of genetic abnormalities such as Down’s Syndrome. The test involves taking a tiny amount of the placental fluid surrounding the developing child with a special syringe. It offers close to 100% detection rate with a stastically insignificant false positive rate.

atlanto-axial instability – instability in the atlanto-axial joint, which is a vital and complicated vertebrae joint of the spine in the neck.

augmentative and alternative communication (AAC) – attempts to study and compensate for temporary or permanent impairments and limitations for people with severe speech/language disorders and comprehensive disorders, whether the problem be with spoken or written language. Often used in occupational therapy for people with Down’s Syndrome

Brushfield spots – small white or grayish/brown spots on the periphery of the iris in the human eye due to accumulation of connective tissue within the iris. Most commonly seen in children with Down’s Syndrome, but can appear in genetically healthy children as well.

chorionic villi sampling – medical laboratory tested used in prenatal diagnosis of genetic abnormalities such as Down’s Syndrome. The test requires a sample of the chorionic villus, also known as placental tissue, to test in a laboratory.

chromosomal disorder – abnormality of chromosome number or structure. See chromosome

chromosome – organized structures of DNA and proteins that are found in many cells. The human chromosome have 46 large linear nuclear chromosomes normally arranged in 23 pairs. Down’s Syndrome is caused by a complete or partial extra copy of the 21st chromosome.

cognitive ability – The ability to remember and process information. Some areas of cognitive ability are usually affected by Down’s Syndrome.

congenital heart defects – a defect in the structure of the heart and great vessels of a newborn, usually caused by a genetic abnormality.

double transverse palmar crease – double lines extending horizontally across the palm of the hand. A double transverse palmar crease is normal for humans. See single transverse palmar crease.

Down’s Syndrome – a chromosomal disorder caused by the presence of all or part of an extra 21st chromosome in all DNA carrying cells of the body. See trisomy 21, Mosaic Down’s Syndrome

epicanthic fold – a skin fold of the upper eyelid covering the inner corner of the eye, giving eyes a narrower appearance than the actual size of the eye. Commonly seen in people of Asian and some African extractions, and accompanying some genetic abnormalities such as Down’s Syndrome. Almost all children develop it in the womb, but it often goes away after the development of the bridge of the nose.

epilepsy – a common and chronic neurological problem that features recurrent, unprovoked seizures as its most obvious symptom

estriol – one of the three main estrogens produced by the human body. It’s only produced in large amounts during pregnancy when it’s synthesized by the placenta. If estriol levels are particularly low during pregnancy, it may indicate a genetic abnormality in a developing child.

false positive – a positive result on a medical test that is in error. In the case of a false positive diagnosis of Down’s Syndrome, parents may be told that their child might have Down’s Syndrome when in fact the child does not. The error factor in most early genetic tests for Down’s Syndrome is between 3% and 5%, and even smaller with amniocentesis.

false negative – a negative result on a medical test that is in error. In the case of a false negative diagnosis of Down’s Syndrome, parents may be told that their child does not have Down’s Syndrome when in fact the child does. The error factor in most early genetic tests for Down’s Syndrome is between 3% and 5%, and even less with amniocentesis.

fine motor skills – coordination of small muscle movements, usually in the hands, to work in concert with each other and often in concert with the eyes.

flexion furrow – the furrows in the inside skin of the fingers above finger joints. Many people with Down’s Syndrome only have one flexion furrow on the fifth finger (pinkie).

gastroesophageal reflux disease – chronic heartburn or indigestion symptoms and/or mucosal damage produced by abnormal reflux of stomach acids up into the esophagus, the tube leading from the mouth to the stomach.

gross motor skills – the ability to coordinate the movement of large skeletal muscles for purposes such as walking, running, sitting up, crawling and so forth.

human chorionic gonadotropin – a peptide hormone produced during pregnancy, first by the embryo and later by the placenta, used to maintain progesterone levels necessary for preventing miscarriage. Abnormal levels can indicate genetic abnormalities in developing child.

hypotonia – see muscle hypotonia.

immune deficiency – a state in which the body’s ability to fight off infectious disease is either compromised or completely absent.

inhibin Alpha – a peptide hormone that usually participates in the regulation of the human menstrual cycle. Elevated inhibin A at 16-18 weeks of pregnancy, along with other indicators, is used as an early marker of potential Down’s Syndrome.

learning disabilities – a group of disorders that affect a broad range of academic and functional skills including speaking, listening, reading, writing, spelling, reasoning and information organization. Each learning disability is unique and has its own specific requirements for treatment.

leukemia – a form of cancer of the blood or bone marrow. Characterized specifically by the fast proliferation of blood cells, usually white blood cells.

mainstreaming – the practice of bringing special needs students out of isolation in “special schools” and into their age groups in “mainstream” classrooms.

meoitic nondisjunction event – the event of duplication, mutation or deletion of genetic material that creates a genetic abnormality

mosaic Down’s Syndrome – some cells in the body show trisomy 21, while others are genetically normal. Considerable variation in number and effect of the trisomy 21 cells exists in mosaic Down’s Syndrome.

muscle hypotonia – poor muscle tone. Has nothing to do with muscle strength, but rather indicates a miscommunication between the muscle and the cerebellum.

nuchal translucency – the amount of fluid behind the neck, observable on ultrasound scans. Children with Down’s Syndrome tend to have a lot of fluid around the neck during pregnancy.

nuchal translucency/free beta/PAPPA test – a combination of laboratory tests and ultrasound scans that look for the nuchal translucency level along with maternal blood levels of beta human chorionic gonadotropin and pregnancy-associated plasma protein A. This set of tests and scans offers a 91% detection rate with a 5% false positive rate, making it one of the more reliable first trimester tests.

obstructive sleep apnea – pauses in breathing during sleep due to blockage of the airway. Usually happens when the muscles of the airway relax during sleep, creating sleep-related physical blockage.

otitis media – inflammation of the middle ear, just beyond the part that can be visually identified.

palpebral fissures – the anatomic name for the separation between the upper and lower eyelids. In other words, the space between your eyelids that shows your eye when it’s open. Children with Down’s Syndrome tend to have upslanted palpebral fissures.

percutaneous umbilical cord blood sampling – a diagnostic genetic test that examines blood from the umbilical cord to detect abnormalities before birth. This is one of the more invasive but definite genetic tests used to test for Down’s Syndrome.

placenta – the organ that develops to coordinate the transfer of nutrients and oxygen from the mother’s circulatory system to the developing child’s.

pregnancy-associated plasma protein A – a protein structure specifically associated with pregnancy. Abnormal levels, along with abnormal results on other tests, can serve as an early marker for potential Down’s Syndrome.

quad test – A panel of laboratory tests that measures maternal alpha feto protein, estriol, human chorionic gonadotropin and inhibin Alpha (inhibin A) that serves as an early test for Down’s Syndrome. This set of tests is performed between 15 and 20 weeks of pregnancy and offers a 79% detection rate with a 7.5% false positive rate.

retardation – generalized disorder featuring below average cognitive function and deficits in two or more adaptive behaviours. Mild retardation occurs between IQ scores 50 and 70, moderate retardation is classified with IQ scores of 35 to 49, severe retardation is classified with IQ scores between 20 and 34, and profound retardation is classified with IQ scores below 19.

Robertsonian translocation – a common form of chromosomal rearrangement when the entire arm or entire chromosome shifts its place in the DNA strand. One of the genetic methods by which Down’s Syndrome occurs.

single transverse palmar crease – a single crease going horizontally across the palm. Frequent symptom of Down’s Syndrome, but can occur in any human. See double transverse palmar crease.

thyroid dysfunction – any disorder of the thyroid gland, which sits in the throat. If the thyroid produces either too much or too little thyroid hormones, metabolism and development can both be negatively affected.

triple screen – a panel of laboratory tests that measures maternal levels of alpho feto protein, estriol, and human chorionic gonadotropin that serves as an early diagnostic for Down’s Syndrome. It’s performed between 15 and 20 weeks of pregnancy and offers a 75% detection rate with a 8.5% false positive rate.

trisomy 21 – the genetic designation for Down’s Syndrome. Indicates that there is an extra partial or complete copy of chromosome 21, leading to a triad where a pair is supposed to be.

ulnar loop dermatoglyphs – a particular pattern of fingerprints where the loops start on the outside of the fingerpad, on the “pinky side” and loop up and over to create the fingerprint pattern itself. Multiple ulnar loop fingerprints (dermatoglyphs) are another sign of Down’s Syndrome.


Research and Main write by Loni Ice, minor editing by Donald Urquhart

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