In microtia the ear is reduced in size and is abnormal in shape. The malformation is usually one-sided, most often on the right side. The ear channel is often missing and hearing is usually impaired. Little in known about its cause, but there is often a hereditary link implicated, and it was seen in infants damaged by thalidomide and isotretinoin (Vitamin A analogue).
The incidence rates are low for congenital abnormalities (around 1 to 2 births per 10,000). Relative high rates are recorded in China (Sichuan) and South America.