Teprotumumab for dysthyroid optic neuropathy: early functional and structural improvement in a retrospective case series.

Dysthyroid optic neuropathy (DON) is a severe, vision-threatening manifestation of thyroid eye disease. We conducted a retrospective descriptive case series of consecutive patients with DON treated with teprotumumab at a single center to evaluate functional, structural, magnetic resonance imaging (MRI)-based inflammatory, and safety outcomes. Six patients (10 eyes) were included. Eye-level outcomes were assessed at baseline and during follow-up using generalized estimating equations to account for within-patient correlation. The primary outcomes were best-corrected visual acuity (BCVA), expressed as logarithm of the minimum angle of resolution (logMAR) and summed cross-sectional area of the four rectus muscles (CSA). Secondary outcomes were proptosis and mean T2 signal intensity ratio (T2-SIR) of the four rectus muscles. Estimated marginal mean BCVA improved from 0.35 logMAR at baseline to 0.04 at 3 weeks, 0.05 at 12 weeks, and -0.08 at 24 weeks. Summed rectus CSA decreased from 2.11 cm2 at baseline to 1.48 cm2 at 12 weeks and 1.41 cm2 at 24 weeks. Proptosis and mean T2-SIR also decreased during follow-up. Most non-hearing-related adverse events were mild; however, treatment was discontinued in one patient because of diarrhea and in another because of fatigue and tinnitus. American Speech-Language-Hearing Association (ASHA)-defined hearing threshold shifts were identified in at least one ear in all six patients. These findings suggest that teprotumumab was associated with early concordant improvement across functional, anatomic, and MRI-based inflammatory endpoints in patients with DON. Careful monitoring, particularly audiologic assessment, remains essential.