Alopecia Areata is a condition where people lose hair. This study tests a medicine called baricitinib to see if it helps children aged 6 to under 18 with severe hair loss. The study will last over two years and has four parts. First, there’s a 5-week Screening to check if participants qualify. Then, a 36-week Double-Blind Treatment where neither the doctors nor participants know who gets the real medicine or a dummy pill. After, there's a 2-year Long-term Extension where everyone gets the real medicine, and finally, a 4-week Follow-up to see how everyone is doing.

Eligibility: Children must have had severe alopecia areata for at least one year to join, and they must have tried other treatments before. But if they have other hair-loss conditions or serious health issues, they can’t join.

• The study takes a long time, over two years, and involves multiple visits.
• Participants might get the real medicine or a placebo in the beginning.
• Parents and children should consider if they can commit to the long duration and frequent visits.