Campomelic dysplasia is inherited in an autosomal dominant
pattern, which means that one copy of the altered (mutated) gene
in each cell is sufficient to cause the disorder. If an individual has an autosomal dominant condition, with each pregnancy there is a 50% (1 in 2) chance for the embryo to have the condition, and a 50% chance for the embryo to not have the condition. It should be noted that this risk is for each separate pregnancy; it does not mean that 50% of an individual's pregnancies will be affected by the condition.
Most cases of campomelic dysplasia result from new (de novo) mutations
in or near the SOX9
gene and occur in people with no history of the disorder in their family. Rarely, affected individuals inherit a chromosome
abnormality (such as a deletion
, de novo translocation
, or inversion
) near or involving the SOX9
gene from a parent who may or may not show mild signs and symptoms of campomelic dysplasia.
Because most individuals with campomelic dysplasia have the disorder as the result of a de novo mutation, parents of these individuals are not typically affected. However, a few adults have been diagnosed with campomelic dysplasia after the birth of an affected child or the diagnosis of a fetus during pregnancy.
Recurrence in siblings has occurred, and mosaicism
has been reported. Mosaicism is when an individual has two or more cell lines with different genetic or chromosomal make-ups. An individual may have some cells with the mutation and some cells without (including egg or sperm cells) and not have any signs or symptoms of the condition. If some egg or sperm cells carry the mutation or chromosome abnormality, the condition can be inherited by that individual's offspring. Familial translocations (when a whole chromosome or segment of a chromosome becomes attached to or interchanged with another whole chromosome or segment) invloving the SOX9
gene have been reported, but are rare.
The risk to siblings of an affected individual depends on the genetic status of the affected individual's parents. If a non-mosaic parent of the affected individual has signs and symptoms of the condition, the risk to the siblings is 50%. Because parental mosaicism has been reported, the siblings of an affected individual are at an estimated 2%-5% risk, even if the disease-causing mutation found in the affected individual cannot be detected in either parent.
The risk to a child of a parent with a non-mosaic SOX9
gene mutation is 50% (1 in 2). If the parent has a chromosome rearrangement involving SOX9
, the risk would depend on the specific chromosome abnormality.
Last updated: 12/29/2010
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