Hypotrichosis

The main purpose of this study is to determine the efficacy and safety of baricitinib for the treatment of severe or very severe alopecia areata (hair loss) in children from 6 years to less than 18 years of age. The study is divided into 4 periods, a 5-week Screening period, a 36-week Double-Blind Treatment Period, an approximately 2-year Long-term Extension (LTE) Period, and a 4-week Post-treatment Follow-up period. Some individuals may be eligible to receive treatment after completing the LTE, for a maximum of 180 weeks.