49 XXXXY syndrome
Encyclopedia
49, XXXXY Syndrome is an extremely rare, aneuploidic
sex chromosomal abnormality; its frequency is approximately 1 out of 85,000 to 100,000 males.
and four X chromosomes on the 23rd pair, thus having 49 chromosomes rather than the normal 46. As is common with aneuploidy
disorders, 49, XXXXY syndrome is often accompanied by mental retardation
. It can be considered a form of Klinefelter syndrome, or a variant of it.
It is genetic, but not hereditary. This means that while the genes of the parents cause the syndrome, there is a small chance of more than one child having the syndrome. The probability of inheriting the disease is about 1%.
The individuals with this syndrome are males, but 49, XXXXX also exists with similar characteristics as the female version.
Much like Down Syndrome
the mental effects of 49, XXXXY Syndrome vary. Impaired speech and behavioral problems are typical. Those with 49 XXXXY syndrome tend to exhibit infantile secondary sex characteristics with sterility in adulthood and have some skeletal anomalies. Skeletal anomalies include:
The effects also include:
Aneuploidy
Aneuploidy is an abnormal number of chromosomes, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorders . Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division when the chromosomes do not separate...
sex chromosomal abnormality; its frequency is approximately 1 out of 85,000 to 100,000 males.
Pathophysiology
As its name indicates, a person with the syndrome has one Y chromosomeY chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
and four X chromosomes on the 23rd pair, thus having 49 chromosomes rather than the normal 46. As is common with aneuploidy
Aneuploidy
Aneuploidy is an abnormal number of chromosomes, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorders . Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division when the chromosomes do not separate...
disorders, 49, XXXXY syndrome is often accompanied by mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
. It can be considered a form of Klinefelter syndrome, or a variant of it.
It is genetic, but not hereditary. This means that while the genes of the parents cause the syndrome, there is a small chance of more than one child having the syndrome. The probability of inheriting the disease is about 1%.
The individuals with this syndrome are males, but 49, XXXXX also exists with similar characteristics as the female version.
Effects
Aneuploidy is often fatal, but in this case there is "X-inactivation" where the effect of the additional gene dosage due to the presence of extra X chromosomes is greatly reduced.Much like Down Syndrome
Down syndrome
Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
the mental effects of 49, XXXXY Syndrome vary. Impaired speech and behavioral problems are typical. Those with 49 XXXXY syndrome tend to exhibit infantile secondary sex characteristics with sterility in adulthood and have some skeletal anomalies. Skeletal anomalies include:
- Genu valgus
- Pes cavusPes cavusHigh arch is a human foot type in which the sole of the foot is distinctly hollow when bearing weight. That is, there is a fixed plantar flexion of the foot...
- Fifth finger clinodactylyClinodactyly-References:...
The effects also include:
- Cleft palate
- Club feet
- Respiratory conditions
- Short or/and broad neck
- Low birth weight
- Hyperextensible joints
- Short stature
- Narrow shoulders
- Coarse features in older age
- HypertelorismHypertelorismHypertelorism is an abnormally increased distance between two organs or bodily parts, usually referring to an increased distance between the orbits . In this condition the distance between the inner eye corners as well as the distance between the pupils is greater than normal...
- Epicanthal folds
- PrognathismPrognathismPrognathism is a term used to describe the positional relationship of the mandible and/or maxilla to the skeletal base where either of the jaws protrudes beyond a predetermined imaginary line in the coronal plane of the skull. In general dentistry, oral and maxillofacial surgery and orthodontics...
- GynecomastiaGynecomastiaGynecomastia or Gynaecomastia, , is the abnormal development of large mammary glands in males resulting in breast enlargement. The term comes from the Greek γυνή gyné meaning "woman" and μαστός mastós meaning "breast"...
(rare) - Muscular hypotoniaHypotoniaHypotonia is a state of low muscle tone , often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength...
- Hypoplastic genitalia
- Cryptorchidism
- Congenital heart defects
- A very round face in infancy
See also
- AneuploidyAneuploidyAneuploidy is an abnormal number of chromosomes, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorders . Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division when the chromosomes do not separate...
- Turner syndromeTurner syndromeTurner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...
- Klinefelter syndrome
- 49, XXXXX, a similar syndrome related to females