Mitochondrially Encoded 12S RNA (mt-RNR1)

mt-RNR1 is a gene in the mitochondrial DNA that produces a type of ribosome (called 12S rRNA). There are several variations in the mt-RNR1 gene that can change the structure of ribosomes. Some of these changes can make the human ribosome look very similar to the ribosome of bacteria.

A class of antibiotics called aminoglycosides (e.g. amikacin, gentamicin, neomycin, paromomycin, plazomicin, streptomycin, and tobramycin) work by attacking the ribosome of bacteria. In patients who have differences in the mt-RNR1 gene, aminoglycoside antibiotics also attack the human ribosomes. This can put the patient at very high risk of hearing loss from aminoglycoside antibiotics. Clinicians use this information to help guide drug therapy decisions.

Clinicians classify patients into 2 categories based on their mt-RNR1 status to help guide decisions on aminoglycoside use.

Priority phenotype

Increased risk of developing hearing loss due to aminoglycosides – These patients are at very high risk of experiencing permanent hearing loss from aminoglycoside antibiotics, even after a single dose. Aminoglycoside antibiotics should be avoided if possible. About 1 in 500 people have this mt-RNR1 phenotype.

Routine phenotype

Normal risk of developing hearing loss due to aminoglycosides – There is no reason to avoid aminoglycoside antibiotics based on mt-RNR1 phenotype alone. It should be noted that patients in this category can still develop hearing loss from the use of aminoglycoside antibiotics.