Chromosome 11, Partial Trisomy 11q is a rare chromosomal disorder in which the end (distal) portion of the long arm (q) of the 11th chromosome appears three times (trisomy) rather than twice in cells of the body. Although associated symptoms and findings may vary, the disorder is often associated with delayed growth before and after birth (prenatal and postnatal growth retardation); varying degrees of mental retardation; distinctive abnormalities of the skull and facial (craniofacial) region; and/or other features. Chromosomal analysis is necessary for a definite diagnosis.
Chromosome 11, Partial Trisomy 11q is commonly characterized by growth retardation before and after birth, delayed acquisition of skills requiring the coordination of mental and motor activities (psychomotor retardation), mild to moderate mental retardation, and distinctive craniofacial abnormalities.
In individuals with Partial Trisomy 11q, craniofacial abnormalities may include an abnormally small head (microcephaly) that may appear unusually short and broad (brachycephaly); a short nose; low-set ears; and/or incomplete closure of the roof of the mouth (cleft palate) or a highly arched palate. Many affected individuals also have abnormal pits or depressions and/or outgrowths of skin and cartilage in front of the ears (preauricular pits or tags); a small jaw (micrognathia); a retracted lower lip; and/or an unusually long vertical groove in the center of the upper lip (philtrum). Additional craniofacial features may sometimes include widely spaced eyes (ocular hypertelorism); downwardly slanting eyelid folds (palpebral fissures); vertical skin folds over the eyes’ inner corners (epicanthal folds); and/or abnormal deviation of one eye in relation to the other (strabismus). In addition, in some cases, one side of the face may appear smaller than or relatively dissimilar to the other (facial asymmetry).
In some affected individuals, Chromosome 11, Partial Trisomy 11q may also be associated with additional physical findings. These may include skeletal abnormalities, such as malformation of the collarbone (clavicular defect) and/or dislocation or improper development (dysplasia) of the hips; structural malformations of the heart that are present at birth (congenital heart defects); and/or underdevelopment or absence of the band of nerve fibers that normally joins the two hemispheres of the brain (hypoplasia or agenesis of the corpus callosum). Additional abnormalities that have been reported in association with Partial Trisomy 11q have included an unusually short neck; abnormal looseness of the skin (cutis laxa); abnormal creases on the palms of the hands; or undescended testes (cryptorchidism) and/or an unusually small penis (micropenis) in affected males.
In individuals with Chromosome 11, Partial Trisomy 11q, the end (distal) region of the long arm (q) of chromosome 11 is present three times (i.e., trisomic or duplicated) rather than twice in cells of the body. Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as “p” and a long arm identified by the letter “q.” Chromosomes are further subdivided into bands that are numbered.
Evidence suggests that Partial Trisomy 11q typically results from a translocation involving chromosome 11q and another chromosome, usually chromosome 22q. Translocations occur when regions of certain chromosomes break off and are rearranged, resulting in shifting of genetic material and an altered set of chromosomes. In individuals with Partial Trisomy 11q, such translocations most commonly appear to be transmitted by a parent who is a carrier of a “balanced” translocation. If a chromosomal rearrangement is balanced, meaning that it consists of an altered but balanced set of chromosomes, it is usually harmless to the carrier. However, such a chromosomal rearrangement may be associated with an increased risk of abnormal chromosomal development in the carrier’s offspring. Chromosomal analysis may determine whether a parent has a balanced translocation. In a few cases, chromosomal rearrangements resulting in Partial Trisomy 11q have appeared to occur spontaneously for unknown reasons (de novo). In such cases, the parents of the affected child usually have normal chromosomes and a relatively low risk of having another child with the chromosomal abnormality.
Chromosome 11, Partial Trisomy 11q is a very rare chromosomal disorder that is reported to affect more females than males. Approximately 45 cases of this disorder have been documented in the medical literature.
Chromosome 11, Partial Trisomy 11q may be diagnosed through genetic testing, either during pregnancy (prenatally) or after birth (postnatally). Prenatal procedures such as amniocentesis, chorionic villus sampling, and fetal blood sampling involve chromosomal analysis of fluid and/or tissue samples extracted from the fetus or the uterus during pregnancy (prenatally).
Treatment of Chromosome 11, Partial Trisomy 11q is symptomatic and supportive. Special education, physical therapy, and other medical, social, or vocational services are of benefit to the affected individual, and are often necessary for the child to reach his/her full potential. Genetic counseling will be of benefit for affected individuals and their families.
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