Microtia Anotia: Birth Defect Of The Infant’s Ears

Anotia is a rare birth deformity that is characterized by the missing pinna, which is the external fraction of the ear that is visible to the eye. This is not to be mistaken with aural atresia, which is characterized by the missing ear canal. American (1.9-3.4), Asian, Hispanic, and North European babies are more likely to be born with this congenital defect than other nationalities.

Microtia Anotia is classed in four categories, by the severity of the defect.

  • Class I – The auricle appears to be normal, whereas the pinna is smaller in size than the normal infant ear.
  • Class II – A portion of the anatomical ear structures are still visible and noted.
  • Class III – This type (Peanut-Shell) just happens to be the most common configuration. Only a small portion of the soft tissue base is visible.
  • Class IV – The external ear and auditory canal is completely missing, which makes this the most severe class.

Anotia can potentially occur unilaterally in 79-93% of the noted cases (NCBI). The right ear is more often affected than the left ear, in this form, with normal speech, language, and hearing in the opposite unaffected ear. Bilateral cases have also been noted, but is not as prominent.

Other anomalies that are noted in anotia

  • Facial deformities
  • Cleft malformation
  • Heart defects
  • Polydactyly (congenital defect characterized by extra digits on the hand and toes
  • Microphthalmia is characterized by unilateral or bilateral eye deformities. The eye will appear much smaller than normal.
  • Vertebral deformities (involving the spine’s alignment, shape)


There have many causes that may potentially be linked to anotia including:

  • Environmental factors (altitude)
  • Gestational factors (alcohol, retinoid or vitamin A, thalidomide, and immunosuppressant (mycophenolate)
  •  Pregnancy obesity
  • Folic acid supplements
  • Genetic factors

Thalidomide is often prescribed for multiple myeloma, in conjunction with dexamethasone (steroidal inflammatory). It has been linked to many birth defects and embryo fetal deaths. It is advised against prescribing this drug to pregnant females, due to its high adverse side affects and increase risk of congenital defects. Deep vein thrombosis and pulmonary embolism is also linked to the use of the medication.