has part has part characteristic of inheres in has modifier Microtia The definitions of microtia follow a widely used, surgically based, classification of ear anomalies outlined by Weerda 1988. As microtia indicates at least both decreased length and width, and in more severe forms it includes abnormal shape of structures, all forms are acknowledged to be bundled terms, but are retained here because they are well established. Small ears HP:0008550 Hypoplastic ears Underdevelopment of the external ear. HP:0000409 Bilateral microtia HP:0008621 Underdeveloped ears Hypoplastic pinna Hypoplasia of the external ear SNOMEDCT_US:35045004 UMLS:C0152423 HP:0008551 HP:0008618 Small pinnae HP:0000393 Aplasia/Hypoplasia of the external ear abnormal hypoplastic external ear