Syndrome, trisomy 21

Syndrome, trisomy 21
A common chromosome disorder, often called Down syndrome, due to an extra chromosome number 21 (trisomy 21). The chromosome abnormality affects both the physical and intellectual development of the individual. Trisome 21 (Down) syndrome is associated with a major risk for heart malformations, a lesser risk of duodenal atresia (part of the small intestines is not developed), and a minor but still significant risk of acute leukemia. Trisomy 21 is due to an extra copy of chromosome number 21. Instead of having the normal 2 copies of chromosome number 21, the person with Down syndrome has 3 copies of chromosome number 21. Confirmation of such a condition requires a chromosome study (analysis under the microscope of the chromosomes). A chromosome study is also valuable to rule in or out a translocation (a type of rearrangement) of chromosome 21 that can be heritable in which case it can give rise to more cases of Down syndrome in the family. The evaluation of the Down syndrome baby and the family by a medical geneticist is often useful. In Down syndrome there are certain characteristic features in the appearance which may individually be quite subtle but together permit a clinical diagnosis of Down syndrome to be made at birth. These signs of Down syndrome include slight flattening of the face, minimal squaring off of the top of the ear, a low bridge of the nose (lower than the usually flat nasal bridge of the normal newborn), an epicanthal fold (a fold of skin over top of the inner corner of the eye, which can also be seen less frequently in normal babies), a ring of tiny harmless white spots around the iris, and a little narrowing of the palate. There are many, many more minor malformations in Down syndrome. Down syndrome is also associated with a number of major malformations. For example, approximately a half of Down syndrome children are born with a heart defect, most often a hole between the two sides of the heart. For another example, Hirschprung's disease (congenital aganglionic megacolon) which can cause intestinal obstruction occurs more frequently in children with Down syndrome than in other children. The intellectual handicaps in Down syndrome are often the most important problem. These handicaps may not be evident in early infancy. However, they tend to become increasingly noticeable later in infancy and during childhood as developmental delay. In adults with Down syndrome, the intellectual handicap is manifest as mental retardation. Very few adults with Down syndrome can lead independent lives because of their mental retardation. It was once thought that nearly all adults with Down syndrome developed Alzheimer's disease (dementia) so that on top of their mental handicap most people with Down syndrome were slated for premature senility. However, it now appears that a much lower proportion, perhaps 20 to 25%, of Down's adults develop dementia. The majority of adults with Down syndrome may thus be spared this fate. The name Down syndrome refers to a 19th century English physician Langdon Down. Ironically, he was not the first person to describe the condition, he added little to our knowledge of it and, in great error, he attributed the condition to a "reversion" to the mongoloid race. The disorder was also once called mongolism, a term now considered obsolete.

Medical dictionary. 2011.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Syndrome, trisomy 13 — Condition with three rather than the normal two chromosomes #13. Children born with this syndrome have multiple malformations and mental retardation due to the extra chromosome #13. The congenital malformations (birth defects) commonly include… …   Medical dictionary

  • Syndrome, trisomy 18 — There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head… …   Medical dictionary

  • Patau syndrome (trisomy 13 syndrome) — A syndrome characterized by multiple malformations, commonly including scalp defects, hemangiomas (blood vessel malformations) of the face and nape of the neck, cleft lip and palate, malformations of the heart and abdominal organs, and flexed… …   Medical dictionary

  • Trisomy — ICD9 = ICDO = OMIM = MedlinePlus = eMedicineSubj = eMedicineTopic = MeshID = D014314A trisomy is a form of aneuploidy with the presence of three copies, instead of the normal two, of a particular chromosome.cite web… …   Wikipedia

  • trisomy — noun chrosomal abnormality in which there is one more than the normal number of chromosomes in a cell • Hypernyms: ↑chromosomal aberration, ↑chromosomal anomaly, ↑chrosomal abnormality, ↑chromosonal disorder • Hyponyms: ↑mongolism, ↑mongolianism …   Useful english dictionary

  • Syndrome, Patau — Trisomy 13 syndrome or three chromosome number 13s instead of the normal two. Children with this condition have multiple malformations and mental retardation due to an extra chromosome #13 Named after the late Klaus Patau who described the extra… …   Medical dictionary

  • Trisomy 9 — is a chromosomal disorder caused by having three copies (trisomy) of chromosome number 9. It can appear with or without mosaicism. ymptomsSymptoms vary, but usually result in dysmorphisms in the skull, nervous system, and mental retardation.… …   Wikipedia

  • trisomy 13 — n. The condition of having three copies of chromosome 13 that results in a syndrome characterized by mental retardation and defects to the central nervous system and heart. * * * also called  Patau s Syndrome,        human chromosomal disorder… …   Universalium

  • Syndrome de down — « trisomie 21 » redirige ici. Pour les autres significations, voir Trisomie 21 (groupe) …   Wikipédia en Français

  • trisomy 13 — thər(t) tēn n a congenital condition that is characterized esp. by usu. severe mental retardation and by craniofacial, cardiac, ocular, and cerebral abnormalities, is caused by trisomy of the human chromosome numbered 13, and is typically fatal… …   Medical dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”