Teprotumumab-associated persistent unilateral hearing loss in dysthyroid optic neuropathy: a case report with review of the literature.

We report a case of severe thyroid eye disease (TED) complicated by dysthyroid optic neuropathy (DON) in a 55-year-old woman with Graves' disease. Despite insufficient response to high-dose intravenous steroid therapy, teprotumumab led to marked improvement in proptosis, orbital inflammation, and visual function. However, treatment was associated with progressive and persistent sensorineural hearing loss after completing eight infusions. Auditory symptoms began after the fifth infusion with intermittent aural fullness and sound reverberation, progressing to mild down-sloping sensorineural hearing loss. Nine days after the final infusion, the four-frequency pure-tone average (PTA4) was 21.25 dB hearing level (HL) in the right ear and 27.50 dB HL in the left ear. Despite initiation of oral prednisolone therapy (40 mg/day with tapering), progressive hearing loss was observed in the right ear, particularly in the low- to mid-frequency range (250-2,000 Hz), with thresholds worsening to 90 dB HL. At twenty days after the final infusion, PTA4 had increased to 75.00 dB HL in the right ear and 31.25 dB HL in the left ear. Serial audiometric assessments at 107, 128, and 198 days after the final infusion demonstrated no recovery. The patient's history of sudden sensorineural hearing loss suggests increased susceptibility to teprotumumab-associated ototoxicity. This case underscores the importance of individualized risk assessment, careful audiologic monitoring, and shared decision-making when balancing visual recovery against the risk of potentially irreversible auditory toxicity.