Genetics of Microtia
Is missing ear cartilage genetic? It is believed that genetics of ear cartilage play a role in the occurrence of microtia. Based on different studies, there exists a wide range of 3% to 34% of familial cases out of the total microtia cases. Moreover, several studies also reported hereditary forms of this ear deformity with autosomal recessive or dominant mode of inheritance with incomplete penetrance and variable expression.
Genetics can be the clear cut cause of the problem. The already identified missing ear cartilage genetic problems include the trisomy of chromosomes 13, 18, and 22. Complex chromosomal rearrangements, microldeletions, and distinct hereditary genomic copy number variants were also implicated to be causes of this deformity.
There are cases where complex genetic problems can also lead to other associated syndromes aside from the missing cartilage in the ear. The chromosomal translocations affecting the 6p24 region have also been linked to bilateral microtia and associated facial deformity like orofacial clefting. In the case of Treacher Collins syndrome, the absence of cartilage in both ears and the deformities in other facial structures can be attributed to the mutation in the Treacher Collins-Franceschetti 1 or TCOF1 gene.
In other cases, the genetic cause can only be inferred as a possible cause. Microtia can demonstrate an inherited pattern among several family members but the specific genes causing the problem may not be identified by science. Furthermore, some ethnic groups have higher chances of having the condition. Nevertheless, this does not prove a genetic population disposition.