Tag Archives: Aneuploidy

Klinefelter’s Syndrome

Definition:
Klinefelter’s syndrome is a chromosomal abnormality that affects males who carry an extra one or more X chromosomes. Females have XX chromosomes and males have XY chromosomes. A male with Klinefelter’s would have XXY or XXXY. Because of the extra chromosome, individuals with the condition are usually referred to as “XXY Males”, or “47, XXY Males. It can lead to a variety of physical and physiological characteristics……CLICK & SEE THE PICTURES

Klinefelter syndrome is the most common sex chromosome disorder in males and the second most common condition caused by the presence of extra chromosomes. The condition exists in roughly 1 out of every 650 males.  One in every 500 males has an extra X chromosome but does not have the syndrome. Other mammals also have the XXY syndrome, including mice.

The syndrome can affect different stages of physical, language and social development .Principal effects sometimes include development of small testicles and reduced fertility. Because they often don’t make as much of the male hormone testosterone as other boys, teenagers with Klinefelter’s syndrome may have less facial and body hair and may be less muscular than other boys. They may have trouble using language to express themselves. They may be shy and have trouble fitting in.

The syndrome was named after Dr. Harry Klinefelter, who in 1942 worked with Fuller Albright at Massachusetts General Hospital in Boston, Massachusetts and first described it in the same year.

Symptoms:
XXY occurs in approximately 1 out of 1,000 live male births, but many men with it do not develop KS. When KS does develop, it usually goes undetected until puberty or sometimes much later.

Characteristics may include:

•For babies:
*Smaller birth weight and slower muscle and motor development
•For children and adults:
*Tallness with extra long arms and legs
*Abnormal body proportions (long legs, short trunk)
*Enlarged breasts (common)
*Lack of facial and body hair
*Small firm testes, small penis
*Lack of ability to produce sperm (common)
*Diminished sex drive, sexual dysfunction
*Social and learning disabilities (common)
*Personality impairment
*Attention deficit hyperactivity disorder (ADHD)
*Normal to borderline IQ
*Speech and language problems—Children with KS often learn to speak later than other children. They may have a difficult time reading and writing.

Men with KS have an increased risk of:

•Type 2 diabetes
•Breast cancer
•Lung cancer
•Cardiovascular disease
•Lung disease
•Osteoporosis
•Hypothyroidism
•Dental problems
•Leg ulcers

In contrast to these potentially increased risks, it is currently thought that rare X-linked recessive conditions occur less frequently in XXY males than in normal XY males, since these conditions are transmitted by genes on the X chromosome, and people with two X chromosomes are typically only carriers rather than affected by these X-linked recessive conditions.

There are many variances within the XXY population, just as in the most common 46,XY population. While it is possible to characterise 47,XXY males with certain body types, that in itself should not be the method of identification as to whether or not someone has 47,XXY. The only reliable method of identification is karyotype

Cause:
The extra X chromosome is retained because of a nondisjunction event during meiosis I (gametogenesis). Nondisjunction occurs with when homologous chromosomes, in the case the X and Y sex chromosomes, fail to separate, producing a sperm with an X and a Y chromosome. Fertilizing a normal (X) egg produces an XXY offspring.

The XXY chromosome arrangement is one of the most common genetic variations from the XY karyotype, occurring in about 1 in 500 live male births.

Another mechanism for retaining the extra X chromosome is through a nondisjunction event during meiosis II in the female. Nondisjunction will occur when sister chromatids on the sex chromosome, in this case an X and an X, fail to separate. An XX egg is produced which, when fertilized with a Y sperm, yields XXY offspring.

In mammals with more than one X chromosome, the genes on all but one X chromosome are not expressed; this is known as X inactivation. This happens in XXY males as well as normal XX females. However, in XXY males, a few genes located in the pseudoautosomal regions of their X chromosomes, have corresponding genes on their Y chromosome and are capable of being expressed. These triploid genes in XXY males may be responsible for symptoms associated with Klinefelter syndrome.

The first published report of a man with a 47,XXY karyotype was by Patricia A. Jacobs and Dr. J.A. Strong at Western General Hospital in Edinburgh, Scotland in 1959. This karyotype was found in a 24-year-old man who had signs of Klinefelter syndrome. Dr. Jacobs described her discovery of this first reported human or mammalian chromosome aneuploidy in her 1981 William Allan Memorial Award address

Variations:
The 48, XXYY (male) syndrome occurs in 1 in 18,000–40,000 births and has traditionally been considered to be a variation of Klinefelter syndrome. XXYY tetrasomy is no longer generally considered a variation of KS,[citation needed] although it has not yet been assigned an ICD-10 code.

Males with Klinefelter syndrome may have a mosaic 47,XXY/46,XY constitutional karyotype and varying degrees of spermatogenic failure. Mosaicism 47,XXY/46,XX with clinical features suggestive of Klinefelter syndrome is very rare. Thus far, only about 10 cases have been described in literature

Risk Factors:
Cases are sporadic but there’s an increased risk in the children of older mothers. Older mothers at risk may be offered pre-natal tests.

Diagnosis:
A karyotype is used to confirm the diagnosis. In this procedure, a small blood sample is drawn. White blood cells are then separated from the sample, mixed with tissue culture medium, incubated, and checked for chromosomal abnormalities, such as an extra X chromosome.

Diagnosis can also be made prenatally via chorionic villus sampling or amniocentesis, tests in which fetal tissue is extracted and the fetal DNA is examined for genetic abnormalities. A 2002 literature review of elective abortion rates found that approximately 58% of pregnancies in the United States with a diagnosis of Klinefelter syndrome were terminated

Treatment:
The genetic variation is irreversible. Testosterone treatment is an option for some individuals who desire a more masculine appearance and identity.(but testosterone replacement therapy may induce a more male appearance and reduce the risk of osteoporosis in many cases. Fertility can often be accomplished with fertility treatment.)

Often individuals that have noticeable breast tissue or hypogonadism experience depression and/or social anxiety because they are outside of social norms. This is academically referred to as psychosocial morbidity. At least one study indicates that planned and timed support should be provided for young men with Klinefelter syndrome to ameliorate current poor psychosocial outcomes.

By 2010 over 100 successful pregnancies have been reported using IVF technology with surgically removed sperm material from men with Klinefelter syndrome

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose

Resources:
http://en.wikipedia.org/wiki/Klinefelter’s_syndrome
http://www.bbc.co.uk/health/physical_health/conditions/klinefelter1.shtml

http://www.aurorahealthcare.org/yourhealth/healthgate/getcontent.asp?URLhealthgate=11722.html

Enhanced by Zemanta
Advertisements

Edward’s syndrome

 

Alternative Names:Trisomy 18 (T18), Trisomy E or Edwards syndrome

Definition:
Edward’s syndrome is a genetic disorder caused by the presence of all or part of an extra 18th chromosome. It is named after John H. Edwards, who first described the syndrome in 1960. It is the second most common autosomal trisomy, after Down Syndrome, that carries to term.

click & see the pictures

A rare genetic chromosomal syndrome where the child has an extra third copy of chromosome 18.
Trisomy 18 is caused by the presence of three – as opposed to two – copies of chromosome 18 in a fetus or infant‘s cells. The incidence of the syndrome is estimated as one in 3,000 live births. The incidence increases as the mother’s age increases.  Edwards syndrome is more severe than the more common Down syndrome. Edwards syndrome causes mental retardation and numerous physical defects that often cause an early infant death.The syndrome has a very low rate of survival, resulting from heart abnormalities, kidney malformations, and other internal organ disorders. Most fetuses are aborted before term, but a live birth with this condition occurs with a frequency around 1-in-3000.

Edwards’ syndrome occurs in around one in 6,000 live births and around 80 per cent of those affected are female. However, the majority of babies with the syndrome die before birth.

It affects people from all cultural backgrounds and becomes more likely with increasing maternal age.

Symptoms:
The features and problems that develop in children with Edwards’ syndrome vary from child to child.

Typically, a child will have a small head with characteristic facial features including a small jaw and mouth, upturned nose, widely spaced small eyes with narrow eyelid folds and drooping of the upper eyelids, and low-set, malformed ears.

The hands may be clenched, with the second and fifth fingers overlapping the other fingers, and the thumbs may be underdeveloped or absent. Webbing of the second and third toes may also occur.

In addition to these features, all systems of the body may be affected. Structural malformations of the heart, kidneys, brain, digestive tract and genitals may be present and cause the child difficulties. For example, children with the syndrome often have trouble feeding and breathing, and experience delay in growth and development. Infections of the lungs and urinary system are also common.

Diagnosis:
At birth, if physical characteristics suggest the possibility of Edwards’ syndrome, this can be confirmed with genetic testing.

An ultrasound during pregnancy can often identify foetal abnormalities, providing the opportunity for genetic testing by amniocentesis.

Treatment:
There’s no cure for Edwards’ syndrome, but medical treatment of symptoms is provided as required.

Treatment focuses on providing good nutrition, tackling infections – which arise frequently – and helping the heart to function better.

Many babies with Edwards’ syndrome have difficulties with feeding, so food may be given via a nasogastric tube or directly into the stomach through a gastrostomy. Where limb abnormalities affect movement, physiotherapy and occupational therapy can help.

Emotional support for parents and other members of the family is vital, as babies with Edwards’ syndrome have a shortened life expectancy. Few survive beyond their first year.

Prognosis:
In England and Wales, there were 495 diagnoses of Edwards’ syndrome (trisomy 18) in 2008/2009, of which 92% were made prenatally. There were 339 terminations, 49 stillbirths/miscarriages/fetal deaths, 72 unknown outcomes, and 35 live births. Because approximately 3% of cases of Edwards’ syndrome with unknown outcomes are likely to result in a live birth, the total number of live births is estimated to be 37 (2008/09 data are provisional). Only 50% of liveborn infants live to 2 months, and only 5–10% survive their first year of life. Major causes of death include apnea and heart abnormalities. It is impossible to predict the exact prognosis of a child with Edwards syndrome during pregnancy or the neonatal period. The median lifespan is 5–15 days. One percent of children born with this syndrome live to age 10, typically in less severe cases of the mosaic Edwards syndrome. The small percentage of babies with the full Edwards syndrome who survive birth and early infancy may live to adulthood, and children with mosaic or partial forms of this trisomy may have a completely different and much more hopeful prognosis.

 

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.

Resources:
http://www.ispub.com/journal/the_internet_journal_of_third_world_medicine/volume_4_number_1_53/article/edwards_syndrome_in_a_neonate_from_a_developing_country_reasons_for_concern_a_case_report.html
http://www.netdoctor.co.uk/ate/pregnancyandchildbirth/205249.html
http://www.wrongdiagnosis.com/e/edwards_syndrome/intro.htm
http://en.wikipedia.org/wiki/Edwards_syndrome
http://www.bbc.co.uk/health/physical_health/conditions/edwardssyndrome2.shtml

Enhanced by Zemanta