Incidence Trends and Severe in-Hospital Outcomes of Pemphigus Vulgaris: A Nationwide Cohort Study.

Contemporary population-based data on incidence trends and in-hospital outcomes of pemphigus vulgaris remain limited, particularly in Southeast Asia. This study aimed to characterize incidence patterns and identify factors associated with severe in-hospital outcomes. We conducted a nationwide retrospective cohort study using Thailand's national administrative health database from 2015 to 2024. Incident cases were defined using a two-year washout period. Crude and age-standardized incidence rates were estimated, and temporal trends were evaluated using Poisson regression. Hospitalization analyses were restricted to index hospitalizations. Severe in-hospital outcomes were defined as a composite of in-hospital mortality, invasive mechanical ventilation, renal replacement therapy, or shock. Associations with severe in-hospital outcomes were evaluated using multivariable logistic regression, with sensitivity analyses accounting for repeated admissions using generalized estimating equations. A total of 2 542 incident adult cases were identified, corresponding to a mean annual incidence of 6.03 per 1 000 000 population. Incidence increased over time (adjusted incidence rate ratio 1.20; 95% CI 1.18-1.22), was higher with advancing age, and among females (female-to-male ratio 1.41:1). Increasing age-standardized incidence rates suggested that the temporal increase was not fully explained by population aging. This trend was accompanied by increasing annual hospitalizations. Among 1 537 index hospitalizations, 8.1% experienced severe in-hospital outcomes. Acute kidney injury, malnutrition, and infection were associated with severe in-hospital outcomes. In sensitivity analyses accounting for repeated admissions, advancing age and cardiovascular comorbidity were also associated with increased risk. Pemphigus vulgaris demonstrates a rising incidence beyond the effects of population aging, accompanied by increasing hospitalizations and a growing burden of severe in-hospital outcomes. These findings support early identification of high-risk patients and appropriate clinical management.