Risk of Osteonecrosis in Vogt–Koyanagi–Harada Patients with Varying Cumulative Corticosteroid Dosages in the First 3 Months: A Nationwide Population-Based Cohort Study

Background: To compare the risk of osteonecrosis (ON) among patients with Vogt–Koyanagi–Harada (VKH) receiving varying cumulative corticosteroid dosages and to evaluate changes in risk over time. Methods: We retrospectively analyzed data from 1,512 patients with VKH in Taiwan’s National Health Insurance Research Database from 2000 to 2019. Patients were categorized based on cumulative prednisone-equivalent dosages in the first 3 months of treatment as follows: low dose (n = 544; 0 < dose ≤ 2 g), medium dose (n = 369; 2 < dose ≤ 4 g), high dose (n = 332; > 4 g), and non-users (n = 267; 0 g). Results: Among VKH patients, combined immunotherapy (IMT) was used in 13.1% within 3 months. After adjustments for age, sex, Charlson Comorbidity Index score, disease stage and the IMT use within the first 3 months, the cumulative risk of ON became significant in the fourth and fifth years for both the low-dose group (HR = 4.59, p = 0.047) and the high-dose group (HR = 5.02, p = 0.043). Conclusions: In this study, only 13.1% of VKH patients received combined IMT within the first 3 months, indicating substantial room to increase early IMT utilization. Early use of combination therapy may potentially reduce corticosteroid exposure, lower the risk of ON, and improve visual outcomes. Patients should be informed of the prolonged risk of corticosteroid-induced ON, which can persist for up to four years, to ensure appropriate monitoring and prevention.