Microtia usually appears in combination with obstruction (atresia) of the external ear canal, and in about 50% of the cases it appears as a single defect with no other accompanying abnormalities.
Treacher Colins Syndrome
In some cases, microtia can appear in combination with other abnormalities which are not associated with any other syndrome, such as:
Cleft lip and palate
Congenital heart diseases
Abnormalities in the kidneys