MedGen

Microtia-anotia (M-A) can occur either as an isolated defect or in association with other defects. Only in a minority of cases has a genetic or environmental cause been found; in these cases, M-A is usually part of a specific pattern of multiple congenital anomalies. For instance, M-A is an essential component of isotretinoin embryopathy (243440), is an important manifestation of thalidomide embryopathy, and can be part of the prenatal alcohol syndrome and maternal diabetes embryopathy. M-A occurs with a number of single gene disorders, such as Treacher Collins syndrome (154500), branchiootorenal/branchiootic syndromes (see 113650 and 602588), oculoauricular syndrome (612109), microtia with hearing impairment and cleft palate (612290), or chromosomal syndromes, such as trisomy 18. M-A also occurs as part of seemingly nonrandom patterns of multiple defects, such as Goldenhar syndrome (164210) (Mastroiacovo et al., 1995). Alasti and Van Camp (2009) reviewed the genetics of microtia and microtia-associated syndromes and discussed their clinical aspects in relation to the causative genes. They stated that the estimated prevalence of microtia is 0.8 to 4.2 per 10,000 births, that it is more common in males, and that it can have a genetic or environmental predisposition. Reviews Ronde et al. (2023) reviewed the international classification and clinical management strategies for craniofacial microsomia and microtia (CFM; see 164210), and tabulated survey responses from 57 professionals involved in management of CFM patients. The authors noted that although the International Consortium for Health Outcomes Measurement (ICHOM) criteria for CFM exclude isolated microtia from the phenotypic spectrum of CFM, the question of whether isolated microtia can be considered the mildest form of CFM is debated in the literature. No consensus was reached in their survey, as a majority of respondents agreed with the ICHOM criteria but also considered isolated microtia to be a mild form of CFM. [from OMIM]