A novel mitochondrial mutation, 1556CT, in a Japanese patient with streptomycin-induced tinnitus

Objective Aminoglycoside antibiotics are associated with ototoxicity. The 1555AG mutation in the 12S ribosomal RNA gene of mitochondrial DNA has been considered to be associated with susceptibility to aminoglycoside antibiotics. In this study we examined a 79-year-old Japanese patient with a 45-year history of streptomycin-induced tinnitus in an attempt to find a mitochondrial mutation. Materials and Methods DNA was extracted from the patient's leukocytes. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) screening for the 1555AG mutation was done in order to detect a mitochondrial mutation and then nucleotide sequencing analysis was performed to identify the mutation. Results PCR-RFLP screening detected the presence of a mitochondrial mutation in the patient. However, the nucleotide sequencing analysis showed that the mutation was not the 1555AG mutation but a novel mutation, 1556CT. The mutation was not found in 112 unrelated Japanese control subjects, suggesting that the mutation was specific to our patient. Conclusions The 1556CT mutation may be a genetic risk factor for aminoglycoside-induced hearing impairment. Our result also suggests that patients with the 1556CT mutation exist among those expected to have the 1555AG mutation as a result of PCR-RFLP analysis.