Damages to the ear are very diverse and can depend on the type of inherited metabolic diseases (IMD). Indeed, IMDs can affect all parts of the auditory system, from the outer ear to the central auditory process. We have identified 219 IMDs associated with various types of ear involvement which we classified into five groups according to the lesion site of the auditory system: congenital external ear abnormalities, acquired external ear abnormalities, middle ear involvement, inner ear or retrocochlear involvement, and unspecified hearing loss. This represents the ninth issue in a series of educational summaries providing a comprehensive and updated list of metabolic differential diagnoses according to system involvement. • We found 219 IMDs associated with various types of ear involvement and provide a list of tests to aid in their diagnosis. • This is the ninth in a series of educational summaries providing a comprehensive list of metabolic differential diagnoses. • This list will be curated and updated on a continual basis in the IEMbase website. [ABSTRACT FROM AUTHOR]