Última actualización:
March 30, 2008
Años publicados: 1992, 1997, 2005
Pallister W syndrome is a rare genetic disorder characterized by unusual facial features such as clefting of the palate and the upper lip, a broad flat nose, widely spaced slanted eyes, and/or downslanting eyelid folds (palpebral fissures). Other symptoms may include mental retardation, speech problems, bone deformities of the arms and legs, and/or seizures. The exact cause of Pallister W syndrome is not known.
Pallister W syndrome is apparent at birth. It is characterized by widely spaced eyes (hypertelorism) with downward slanting eyelid folds (palpebral fissures), a broad flat nasal bridge, a broad tip of the nose, a broad flat jaw, central clefting of the palate or upper lip, seizures, and mental retardation. There may also be bone abnormalities in the arms and legs such as abnormal deviation of the elbow away from the body when the arm is extended (cubitus valgus). Other symptoms may include hair that does not lie flat on the head (cowlick), missing teeth (partial adontia), broad uvula, and a high broad forehead. Additional findings may include tremor and/or involuntary muscle contractions (i.e., spasticity).
The exact cause of Pallister W syndrome is not known. The disorder is thought to be inherited as a X-linked genetic trait. Geneticists interested in this disorder cannot agree about whether genetic transmission follows the rules of dominant or recessive inheritance patterns.
Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 11p13” refers to band 13 on the short arm of chromosome 11. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
Genetic diseases are determined by the combination of genes for a particular
trait that are on the chromosomes received from the father and the mother.
X-linked recessive genetic disorders are conditions caused by an abnormal gene on the X chromosome. Females have two X chromosomes but one of the X chromosomes is “turned off” and all of the genes on that chromosome are inactivated. Females who have a disease gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms of the disorder because it is usually the X chromosome with the abnormal gene that is “turned off”. A male has one X chromosome and if he inherits an X chromosome that contains a disease gene, he will develop the disease. Males with X-linked disorders pass the disease gene to all of their daughters, who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring. Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease, and a 25% chance to have an unaffected son.
X-linked dominant disorders are also caused by an abnormal gene on the X chromosome, but in these rare conditions, females with an abnormal gene are affected with the disease. Males with an abnormal gene are more severely affected than females, and many of these males do not survive.
Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.
All individuals carry a few abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.
Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.
Pallister W syndrome is a very rare disorder. As of the year 2000, only six cases had been reported in the medical literature. More than half involved male infants but the numbers are not large enough to draw any conclusions regarding whether it affects one sex more than the other.
The characteristic facial features assist in the diagnosis.
Treatment
Treatment of Pallister W syndrome may consist of surgery to repair the clefting of the palate and lip, and to repair deformities of the arms and legs if necessary.. Anti-seizure medication may be prescribed to control seizures. Special education and related services will be helpful in school, and speech therapy may be required after surgical repair of the cleft palate.
Genetic counseling may be of benefit for patients and their families. Other treatment is symptomatic and supportive.
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TEXTBOOKS
Gorlin RJ, Cohen MMJr, Levin LS., eds. Syndromes of the Head and Neck. 3rd ed. Oxford University Press, London, UK; 1990:765-66
JOURNAL ARTICLES
Kubota T. [Pallister-W syndrome]. Ryoikibetsu Shokogun Shirizu. 2001;(34 Pt 2):466. [Article in Japanes].
Goizet C, Bonneau D, Lacombe D. W syndrome: report of three cases and review. Am J Med Genet. 1999;87:446-49.
Bottani A, Schinzel A. A third patient with median cleft upper lip, mental retardation and pugilistic facies (W syndrome): corroboration of a hitherto private syndrome. Clin Dysmorphol. 1993;2:225-31.
FROM THE INTERNET
McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Pallister W Syndrome. Entry Number; 311450: Last Edit Date; 12/29/1999.
Pallister syndrome 1. Multiple Congenital Anomaly/Mental Retardation (MCA/MR) Syndromes. nd. 1p.
www.nlm.nih.gov/cgi/jablonski/syndrome_cgi?term=W+syndrome&field=name
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