Down syndrome

Down's syndrometrisomy 21Downs SyndromeDown’s SyndromeDownmongolismDSmongMongoloid21 trisomy syndrome
Down syndrome (DS or DNS), also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21.wikipedia
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Intellectual disability

mental retardationintellectually disabledintellectual disabilities
It is usually associated with physical growth delays, mild to moderate intellectual disability, and characteristic facial features.
Down syndrome and fragile X syndrome are examples of syndromic intellectual disabilities.

Genetic testing

DNA testingDNA analysisDNA test
Down syndrome can be identified during pregnancy by prenatal screening followed by diagnostic testing or after birth by direct observation and genetic testing.
Deviations from the expected number of chromosomes (46 in humans) could lead to a diagnosis of certain genetic conditions such as trisomy 21 (Down syndrome) or monosomy X (Turner syndrome).

John Langdon Down

Langdon DownJohn L. Down
It is named after John Langdon Down, a British doctor who fully described the syndrome in 1866.
John Langdon Haydon Down (18 November 1828 – 7 October 1896) was a British physician best known for his description of the genetic condition now known as Down syndrome, which he originally classified in 1862.

Leukemia

leukaemialeukemiasleukemic
They have an increased risk of a number of other health problems, including congenital heart defect, epilepsy, leukemia, thyroid diseases, and mental disorders.
Risk factors include smoking, ionizing radiation, some chemicals (such as benzene), prior chemotherapy, and Down syndrome.

Congenital heart defect

congenital heart diseasecongenital heart defectsheart defect
They have an increased risk of a number of other health problems, including congenital heart defect, epilepsy, leukemia, thyroid diseases, and mental disorders.
A number of genetic conditions are associated with heart defects, including Down syndrome, Turner syndrome, and Marfan syndrome.

Chromosome abnormality

chromosomal abnormalitieschromosome abnormalitieschromosomal abnormality
Down syndrome is one of the most common chromosome abnormalities in humans.
An example of trisomy in humans is Down syndrome, which is a developmental disorder caused by an extra copy of chromosome 21; the disorder is therefore also called trisomy 21.

Single transverse palmar crease

Simian creaseAbnormal palmar creasespalm prints
People with Down syndrome may have some or all of these physical characteristics: a small chin, slanted eyes, poor muscle tone, a flat nasal bridge, a single crease of the palm, and a protruding tongue due to a small mouth and relatively large tongue.
The presence of a single transverse palmar crease can be, but is not always, a symptom associated with abnormal medical conditions, such as fetal alcohol syndrome, or with genetic chromosomal abnormalities, including Down syndrome (chromosome 21), cri du chat syndrome (chromosome 5), Klinefelter syndrome, Wolf-Hirschhorn Syndrome, Noonan syndrome (chromosome 12), Patau syndrome (chromosome 13), IDIC 15/Dup15q (chromosome 15), Edward's syndrome (chromosome 18), and Aarskog-Scott syndrome (X-linked recessive), or autosomal recessive disorder, such as Leukocyte adhesion deficiency-2 (LAD2).

Epilepsy

epilepticseizure disorderepilepsies
They have an increased risk of a number of other health problems, including congenital heart defect, epilepsy, leukemia, thyroid diseases, and mental disorders.
Between 1 and 10% of those with Down syndrome and 90% of those with Angelman syndrome have epilepsy.

Obstructive sleep apnea

obstructive sleep apnea syndromeobstructive sleep apnoeaobstructive sleep apnea syndrome or obstructive sleep apnea–hypopnea syndrome
These airway changes lead to obstructive sleep apnea in around half of those with Down syndrome.
Down syndrome is one such syndrome.

Child development

developmentchildhood developmentdevelopmental
It is usually associated with physical growth delays, mild to moderate intellectual disability, and characteristic facial features.
In evocative genetic-environmental correlation, the child's genetically-caused characteristics cause other people to respond in certain ways, providing a different environment than might occur for a genetically-different child; for instance, a child with Down syndrome may be treated more protectively and less challengingly than a non-Down child.

Cryptorchidism

undescended testesundescended testiclecryptorchid

Otitis media

middle ear infectionear infectionsotorrhea
This is often the result of otitis media with effusion which occurs in 50–70% and chronic ear infections which occur in 40 to 60%.
It occurs more commonly among indigenous peoples and those who have cleft lip and palate or Down syndrome.

Acute lymphoblastic leukemia

acute lymphocytic leukemiaacute lymphoblastic leukaemiaALL
Although the overall risk of cancer in DS is not changed, the risk of testicular cancer and certain blood cancers, including acute lymphoblastic leukemia (ALL) and acute megakaryoblastic leukemia (AMKL) is increased while the risk of other non-blood cancers is decreased.
Genetic risk factors may include Down syndrome, Li-Fraumeni syndrome, or neurofibromatosis type 1.

Strabismus

squintcross-eyedheterotropia
Between 20 and 50% have strabismus, in which the two eyes do not move together.
Strabismus can be seen in Down syndrome, Loeys-Dietz syndrome, cerebral palsy, and Edwards syndrome.

Acute megakaryoblastic leukemia

AML-M7megakaryocytic acute leukemia
Although the overall risk of cancer in DS is not changed, the risk of testicular cancer and certain blood cancers, including acute lymphoblastic leukemia (ALL) and acute megakaryoblastic leukemia (AMKL) is increased while the risk of other non-blood cancers is decreased.
These groups are: AMKL occurring in young children with Down syndrome, i.e. DS-AMKL; AMKL occurring in children who do not have Down syndrome, i.e. non-DS-AMKL (also termed pediatric acute megakaryoblastic leukemia or pediatric AMKL); and AMKL occurring in non-DS adults, i.e. adult-AMKL.

Transient myeloproliferative disease

In Down syndrome, AMKL is typically preceded by transient myeloproliferative disease (TMD), a disorder of blood cell production in which non-cancerous megakaryoblasts with a mutation in the GATA1 gene rapidly divide during the later period of pregnancy.
Transient myeloproliferative disease (TMD) occurs in a significant percentage of individuals born with the congenital genetic disorder, Down syndrome.

Hypotonia

low muscle tonefloppy infant syndromepoor muscle tone
People with Down syndrome may have some or all of these physical characteristics: a small chin, slanted eyes, poor muscle tone, a flat nasal bridge, a single crease of the palm, and a protruding tongue due to a small mouth and relatively large tongue.

Tetralogy of Fallot

Fallot's TetralogyTetrology of Fallotblue baby operation
Other problems that may occur include tetralogy of Fallot and patent ductus arteriosus.

Pregnancy

pregnantfirst trimesterpregnant women
Since the introduction of screening, pregnancies with the diagnosis are often terminated.
Ultrasound is used to measure the nuchal fold in order to screen for Down syndrome.

Cataract

cataractscataract surgerycongenital cataracts
Cataracts (cloudiness of the lens of the eye) occur in 15%, and may be present at birth.
Examples of chromosome abnormalities associated with cataracts include 1q21.1 deletion syndrome, cri-du-chat syndrome, Down syndrome, Patau's syndrome, trisomy 18 (Edward's syndrome), and Turner's syndrome, and in the case of neurofibromatosis type 2, juvenile cataract on one or both sides may be noted.

Ventricular septal defect

hole in the heartVSDventricular
Of those with heart disease, about 80% have an atrioventricular septal defect or ventricular septal defect with the former being more common.
Congenital VSDs are frequently associated with other congenital conditions, such as Down syndrome.

GATA1

GATA-1GATA box
In Down syndrome, AMKL is typically preceded by transient myeloproliferative disease (TMD), a disorder of blood cell production in which non-cancerous megakaryoblasts with a mutation in the GATA1 gene rapidly divide during the later period of pregnancy.
These diseases include transient myeloproliferative disorder occurring in Down syndrome, acute megakaryoblastic leukemia occurring in Down syndrome, Diamond-Blackfan anemia, and various combined anemia-thrombocytopenia syndromes including a gray platelet syndrome-type disorder.

Dermatoglyphics

dermatoglyphDermatoglyphicDermatoglyphic anomalies
Other common features include: a flat and wide face, a short neck, excessive joint flexibility, extra space between big toe and second toe, abnormal patterns on the fingertips and short fingers.
In 1945, Lionel Penrose, inspired by the works of Cummins and Midlo, conducted his own dermatoglyphic investigations as a part of his research into Down syndrome and other congenital medical disorders.

Brushfield spots

Brushfield spots (small white or grayish/brown spots on the outer part of the iris) are present in 38 to 85% of individuals.
Brushfield spots are a characteristic feature of the chromosomal disorder Down syndrome or trisomy 21.