What is the pathophysiology of Down's Syndrome?

Question

What are the related effects that a person with Down's Syndrome might have?

Answer 1

DOWN SYNDROME



Definition
Epidemiology
Pathophysiology
Etiology
Clinical Manifestations
Diagnosis
Treatment
Prognosis
Reference Page
Definition:
Also known as trisomy 21, Down syndrome is a genetic disorder causing varying degrees of mental retardation as well as presenting with characteristic congenital abnormalities. It is considered one of the most common causes of human deformity and cognitive delay.31(pp126-129)

Epidemiology:
Down syndrome is one of the most frequently occurring chromosomal abnormalities found in humans, occurring in approximately one out of every 800 to 1,000 live births. At least 20 percent will be stillborn. In the United States over 350,000 people have Down syndrome.36

Pathophysiology:
Down syndrome is a chromosomal disorder in which there are three copies of the 21st chromosome. The most common cause of trisomy 21 is nondisjunction (95%), followed by mosiacism (1-2%) and translocation (3 to 4%).

Nondisjunction is a faulty cell division that occurs before or at conception when a pair of number 21 chromosomes, in either the sperm or the egg, fail to separate. As the embryo develops, the extra chromosome is replicated in every cell of the body. The cause is unknown.

Mosaicism occurs after fertilization when nondisjunction of chromosome 21 takes place during an initial cell division. The result is that some of the cells have 47 chromosomes (the 21st chromosome having 3 copies) and some have 46. Mosaicism causes a more mild form of Down syndrome.

Translocation occurs either before or at conception and involves part of chromosome 21 breaking off during cell division and attaching to another chromosome. The total number of chromosomes remains 46, but because of the additional part of the 21st chromosome, the child will have features of Down syndrome.36,37

Etiology:
A major risk factors for nondisjunctive trisomy 21 is increasing maternal age. Although 80 percent of children born with Down syndrome are born to women under 35 years of age (average 28) , the risk at age 30 is 1 in 1,000 and at age 40 is 9 in 1,000. The risk of having a second child with trisomy 21 or mosaic Down syndrome is about 1 in 100. The risk is higher if one parent is a carrier of a translocated cell.37

Clinical Manifestations:
In general, musculoskeletal abnormalities include: hypotonia; hyperflexibilty/mobility of the joints including instability at the C1-2 joint; hip subluxation or dislocation; scoliosis; and foot deformities such as pes planus.31(pp126-129)

Craniofacial abnormalities include: microbrachycephaly with a flat facial profile and short neck; depressed nasal bridge and a small nose; upslanting palpebral fissures; upward slanting eyes; dysplastic (abnormally shaped) ear; and an enlarged, protruding, tongue.12(pp8-13)

Extremity abnormalities include: a single simian crease across the center of the palm; dysplastic midphalanx of the fifth finger which may have only one flexion crease; and an excessive space between large and second toe.12(pp8-13),31(pp126-129)

Other abnormalities include: Mental retardation (100%); speech and motor delay; cardiac anomalies (40%); GI atresia or stenosis; conductive type hearing loss (65-90%); nystagmus and strabismus (40-60%).

Increased risk for health problems including: leukemia and leukemoid reactions (10 to 20 times higher than the normal population); Alzheimer's disease (approximately 25% of people with Down syndrome will develop this disease opposed to 6% of the general population); increased susceptibility to infection; and respiratory problems.36,37

Diagnosis:
Prenatal diagnosis may involve screening and diagnostic tests. The most commonly used screening tests are the Triple Screen and the Alpha-fetoprotein Plus. These screening tests are typically offered between fifteen and twenty weeks of gestation. They detect about sixty percent of fetuses with Down syndrome
Diagnostic tests include chorionic villus sampling (CVS), amniocentesis, percutaneous umbilical blood sampling (PUBS). These procedures are about 98 to 99 percent accurate in the detection of Down syndrome. CVS is usually performed between 8 and 12 weeks, amniocentesis between 12 and 20 weeks of gestation, and PUBS after 20 weeks. If undiagnosed prenatally, Down syndrome is suspected from the newborn's physical appearance.36

Treatment:
Surgery may be necessary for GI obstructions, cardiac anomalies, and hip dislocations or subluxation. Speech and occupational therapy are important in promoting effective oral motor function, lip closure, and tongue retrusion. Also, speech is often delayed which may be due to the hearing abnormalities requiring an audiologist. Physical therapy includes such aspects as positioning, mobility training, strengthening, promoting stability (orthotics), and developing head control. It is important to note that forceful neck flexion and rotation activities should be avoided because of cervical instability. As with all pediatric cases, early education plays a key role to children with Down syndrome.31(pp126-129)

Prognosis:
Advances in medicine have rendered most of the above health problems treatable, and the majority of people born with Down syndrome today have a life expectancy of fifty-five years. They are active learners and will develop skills needed to attend school, socialize, work, and make a positive contribution to society.36

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What is the pathophysiology of Down's Syndrome?
What are the related effects that a person with Down's Syndrome might have?

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it is the study of physical diease in downs syndrome