A cholesteatoma is an abnormal, noncancerous skin growth that can develop in the middle section of your ear, behind the eardrum. It may be a birth defect, but it’s most commonly caused by repeated middle ear infections.

A cholesteatoma often develops as a cyst, or sac, that sheds layers of old skin. As these dead skin cells accumulate, the growth can increase in size and destroy the delicate bones of the middle ear. This may affect hearing, balance, and the function of facial muscles.