The overall aim of this project is to evaluate the potential study population size of ABBV-951 users and estimate incidence rates for infusion site events using data from Finnish national registers and three wellbeing services counties. The counties included will be HUS, Wellbeing Services County of Pirkanmaa (Pirha), and Wellbeing Services County of Southwest Finland (Varha). This project will include 2 data extractions in 2026 and 2027.