Campomelic dysplasia is inherited
in an autosomal dominant
pattern, which means that one copy of the altered (mutated
in each cell
is enough to cause the disorder. If a person has an autosomal dominant genetic disorder, with each pregnancy, there is a 50% (1 in 2) chance for the embryo to have the genetic disorder, and a 50% chance for the embryo to not have the genetic disorder. 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 genetic disorder.
Most cases of campomelic dysplasia result from new (de novo
in or near the SOX9
gene and occur in people with no history of the genetic disorder in their family. Rarely, people with campomelic dysplasia 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 people with campomelic dysplasia have the disorder as the result of a de novo
mutation, parents of these people usually do not have signs and symptoms of the genetic disorder. 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 a person has two or more cell lines with different genetic or chromosomal make-ups. A person 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 genetic disorder. If some egg or sperm cells carry the mutation or chromosome abnormality
, the genetic disorder can be inherited by that person's children. Familial
translocations (when a whole chromosome or segment of a chromosome becomes attached to or interchanged with another whole chromosome or segment) involving the SOX9
gene have been reported but are rare.
The risk to siblings of a person with campomelic dysplasia depends on the genetic status of the affected person'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 a person with the genetic disorder are at an estimated 2%-5% risk, even if the disease-causing mutation found in the person with campomelic disorder 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.
Because of the complexity of the inheritance of campomelic dysplasia, we recommend speaking with a genetics professional.
Last updated: 4/4/2017