Abstract: 【Abstract】 Objective To evaluate the efficacy of Janus kinase （JAK） inhibitors in the treatment of 5 children with severe alopecia areata, especially those with complicated nail damage. Methods A total of 5 children with severe alopecia areata were enrolled and treated with oral JAK inhibitors （tofacitinib or baricitinib）. The improvement of hair loss was assessed by using the severity of alopecia tool （SALT） at 12, 24, 36, and 48 weeks after the start of treatment. For 3 children with complicated nail damage, the improvement of diseased nails and toenails was evaluated by using the modified nail psoriasis severity index after treatment. During the treatment, adverse reactions were monitored. Results The five children with severe alopecia areata were aged 2 － 11 years, their disease duration ranged from 5 to 120 months, and the treatment with JAK inhibitors lasted 24 － 48 weeks. After 12-week treatment, 2 children achieved a 50% improvement in SALT （SALT50）; after 24-week treatment, 3 achieved SALT95, and 1 achieved SALT75 and then withdrew baricitinib for personal reasons; after 36-week treatment, 3 achieved SALT99, and then received half-dose treatment; after 48-week treatment, 1, 1, 1 and 1 patient achieved SALT99, SALT83, SALT31, and SALT0, respectively, and 2 of them experienced gradually aggravated hair loss 1 - 2 months after the half-dose treatment. Among the 3 children with complicated nail damage, the improvement rates of nail severity index scores were 67.5%, 45.4%, and 25% respectively, and the improvement rates of toenail severity index scores were 42.5%, 71.4%, and 5% respectively after 12-week treatment; after 48-week treatment, the improvement rate of nail severity index scores were 100%, 100%, and 50% respectively, and the improvement rate of toenail severity index scores were 96.2%, 100%, 50% respectively. During the treatment, the uric acid level increased in 2 children, and one of them was accompanied by increased serum levels of low-density lipoprotein cholesterol and high-density lipoprotein cholesterol; 1 suffered from respiratory tract infections twice during the treatment, and was recovered after symptomatic treatment; there were no adverse reactions leading to drug withdrawal. Conclusion JAK inhibitors can be used as a treatment option for severe alopecia areata in children.

Key words: Alopecia areata, Nails, JAK inhibitors, Treatment outcome, Child