Small ears are hereditary

Ears are of different sizes. Some people have very big ears, but some people have very small ears. The size of the ears mostly comes from the influence of family appearance. First of all, people look similar in appearance. This is a very normal phenomenon. Generally, small ears are not very hereditary.

Pathological etiology

Embryology

The pinnae originate from the embryonic first branchial arch (mandibular arch) and second branchial arch (hyoid arch). During the 5th week of the embryo, part of the branchial arch will develop into the auricle, and the auricle will be fully developed between the 5th and 9th weeks of the embryo. In the sixth week of embryogenesis, six hillock-like protrusions appear after the activation and proliferation of the ectoderm and mesenchyme in the mandibular arch and hyoid arch. Hillocks 1, 2, and 3 appear at the tail of the mandibular arch and later form the tragus, helix crus, and upper part of the external helix. Hillocks 4, 5, and 6 appear at the head of the hyoid arch and develop into the antihelix, antitragus, and earlobe. The six hillocks proliferate and fuse to form the convex auricle, and the first branchial cleft is sunken inward to form the external auditory canal. During the development stage of the auricle, the embryo is affected by genetic or external factors and is prone to various developmental malformations of the auricle.

Experimental studies on the embryonic development of the pinna have a history of many years, but the mechanism remains unclear. Among them, the role of neural crest cells (CNCC) in ear development has gradually attracted people's attention. CNCC is a multipotential stem cell and the main cell component of the mesenchyme in the first and second branchial arch regions. An important feature of CNCC is its migration. Studies have found that rupture of the stapedial artery during the development of the middle ear in mice can cause microtia, and CNCC is not migratory. Administration of vitamin A during early pregnancy may interfere with the mobility of CNCC.

Genetics

Congenital microtia can occur alone or as part of a syndrome. Common syndromes include Treacher Collins syndrome, Goldenhar syndrome, Nagar syndrome, and Miller syndrome.

The location and identification of the susceptible gene for congenital microtia is a hot topic and difficulty in current research, but there are no research results so far.

Epidemiology

The incidence of congenital microtia varies in literature reports and is related to both race and region. The latest report shows that the incidence rate in our country is 5.18/10000. It occurs more frequently in males than in females (2:1), with right-sided deformities being more common and bilateral deformities accounting for about 10%. The cause of microtia is still unclear. It is generally believed to be the result of the combined effects of environmental and genetic factors. Among the environmental factors, viral colds in the mother's early pregnancy, severe pregnancy reactions, and toxic substances in home decoration are all possible factors that may lead to microtia. The genetic incidence rate of patients with a family history of microtia is approximately 2.9%-33.8%.