Rapid hair regrowth in a patient with alopecia universalis treated with a JAK3/TEC family kinase inhibitor

History, presentation and initial management
A 12-year-old boy presented with longstanding alopecia universalis (AU) in March 2024, with complete loss of scalp hair corresponding to a Severity of Alo­pecia Tool (SALT) score of 100, as well as loss of all eyebrows, eyelashes, and body hair.

He was previously treated with a topical corticosteroid and minoxidil in April 2023, but the response was sub­optimal. He subsequently started receiv­ing traditional Chinese medicine (TCM) in September 2023. Despite initial im­provement, his condition worsened by December 2023, leading to the discon­tinuation of TCM.

The patient had no personal or family history of autoimmune disorders, systemic diseases, or allergic condi­tions. Initial investigations, including complete blood count, liver and renal function tests, thyroid function tests, immunoglobulin levels, autoimmune markers, and systemic inflammatory markers, were all within normal limits. Screening for hepatitis B and C carrier status, as well as tuberculosis infection, was negative.

A Janus kinase (JAK) inhibitor was initiated in May 2024. After 2 months, partial regrowth of eyebrows was ob­served, primarily on the right side, but there was no regrowth of eyelashes or scalp hair. Additionally, he developed a rash on the scalp. By September 2024, there was eyelash regrowth, increased eyebrow regrowth, and patchy hair re­growth on the scalp.

Treatment with ritlecitinib
In September 2024, the patient (SALT 50) was switched to ritlecitinib 50 mg QD as it had become available in Hong Kong through a medication ac­cess programme. By November 2024, following 2 months of ritlecitinib treat­ment, there was ongoing regrowth of eyelashes and eyebrows, along with improvement in scalp hair regrowth (SALT 40).

In February 2025, his SALT score had improved to 0–10 (complete scalp hair regrowth), with complete regrowth of eyebrows and eyelashes. (Figure)

The patient remained on ritlecitinib, although he occasionally missed doses. In June 2025, a small patch of hair loss was observed in the right occipital area (SALT <10), and topical minoxidil was prescribed as localized treatment. Reas­sessment in September 2025 revealed some hair loss in the occipital area (SALT 10–20), and topical mometasone furo­ate was added to his ongoing regimen of oral ritlecitinib and topical minoxidil.

The patient tolerated ritlecitinib well, with no reported adverse effects or significant infections. Following hair regrowth, he demonstrated increased confidence, enhanced eye contact, and greater interest in personal appearance, such as discussing hairstyles.

Discussion
Alopecia areata (AA) is an au­toimmune disorder that tar­gets hair follicles, resulting in non-scarring hair loss. AU is the most severe form of AA, characterized by complete loss of hair on the scalp, face, and entire body. AA significantly impairs quality of life and psychosocial well-being, particularly in children and adolescents.^1-3

Patients with moderate-to-severe AA (SALT ≥20) often require systemic treatment. Conventional systemic ther­apies, including corticosteroids and im­munosuppressants such as cyclospo­rine, methotrexate, and azathioprine, are limited by suboptimal efficacy, safety concerns, and frequent relapses.^2,3

Oral JAK inhibitors (eg, ritlecitinib and baricitinib) are a newer class of targeted small-molecule therapies that offer po­tential for improved treatment outcomes compared with traditional systemic ther­apies for severe AA.^2,4 Ritlecitinib is an oral, selective dual inhibitor of JAK3 and the TEC family of kinases, which modu­lates immune responses to facilitate hair regrowth. It is the first and only first-line systemic treatment approved by both the US FDA and the European Medicines Agency (EMA) for severe AA in patients aged ≥12 years.^2,5 In Hong Kong, ritleci­tinib (50 mg QD) is indicated for treatment of severe AA in adults and adolescents aged ≥12 years, while baricitinib is indi­cated for severe AA in adults only.^6,7

The approval of ritlecitinib for AA was supported by the pivotal phase IIb–III AL­LEGRO trial, which randomized patients aged ≥12 years with AA (SALT ≥50) to re­ceive various dosages of ritlecitinib (50 mg QD group, n=130) or placebo (n=131). At week 24, significantly greater proportions of patients receiving ritlecitinib 50 mg QD vs placebo achieved SALT ≤20 (23 vs 2 percent; p<0.0001) and SALT ≤10 (14 vs 2 percent; p<0.0002). The efficacy of ritlecitinib was sustained over the long term, with 43 percent of patients treated with 50 mg QD achieving SALT ≤20 by week 48.^5,8,9

A network meta-analysis of 13 trials involving 3,613 patients indirectly com­pared the relative efficacy and safety of JAK inhibitors for moderate-to-severe AA. Based on the proportion of patients achieving ≥50 percent improvement in ­SALT score, the surface area under the cumulative ranking curve indicated that ritlecitinib 50 mg ranked among the most effective therapies. Furthermore, ritleci­tinib 50 mg was associated with fewer adverse events (AEs) compared with oth­er high-dose oral JAK inhibitor groups.¹⁰

Like many patients in the ALLEGRO trial, our patient demonstrated marked clinical improvement with ritlecitinib. His SALT score improved from 100 to ≤10 af­ter about 5 months of treatment, accom­panied by complete regrowth of eyelash­es and eyebrows.

Ritlecitinib is generally well tolerated with an acceptable safety profile. In clinical trials, the most common AEs observed with the 50 mg dose included headache (15.1 percent), nasopharyngitis (9.5 per­cent), acne (9 percent), and upper respira­tory tract infection (8.5 percent).¹¹ Ritleci­tinib treatment requires regular monitoring of platelet and lymphocyte counts, along with close surveillance for serious and op­portunistic infections.⁶

As response to treatment after re­lapse may be suboptimal, continuing therapy for at least 6–12 months following complete hair regrowth is recommended before transitioning to maintenance treat­ment or discontinuation.²

Our case and clinical trial data sup­port ritlecitinib’s potential to achieve sustained, near-complete to complete scalp hair regrowth (SALT 0–10), mark­ing a significant therapeutic advancement in AA.