JAK Inhibitor Safety in Atopic Dermatitis and Alopecia Areata: A 4.5-Year Real-World Retrospective Cohort Study

JAK inhibitors (JAKi) represent a novel therapeutic approach for treating the immune-mediated dermatologic diseases alopecia areata (AA) and atopic dermatitis (AD). JAKi have shown a favorable safety profile in controlled clinical trials; however, real-world safety data in routine dermatologic practice remain limited. The objective of this study is to evaluate the safety of JAKis (abrocitinib, baricitinib, upadacitinib, and ritlecitinib) in patients with AA or AD in a real-world setting.

We conducted a single-center retrospective observational study based on electronic medical record data from December 2020 to June 2025. Adult patients with a confirmed diagnosis of atopic dermatitis or alopecia areata who were treated as per routine clinical practice with a dermatologic JAKi were included. Adverse events (AE) were retrospectively collected.

A total of 376 adult patients were included. AE events were observed across all agents and were predominantly mild to moderate. Mild total cholesterol increase, weight gain, and upper respiratory tract infection were the most common AE. Discontinuation was mainly driven by loss of efficacy, while AE-related discontinuations were less frequent and heterogeneous in nature. Importantly, only one case of venous thrombo-embolism was reported in a patient with other thrombotic risk factors, and no cases of major adverse cardiovascular events (MACEs) were recorded. Four cases of malignancies were reported. Notably, sex-specific differences emerged in metabolic adverse events, with weight gain occurring more frequently among female patients. Menstrual alteration, although rare, was a newly described safety event and was the leading cause of treatment discontinuation due to safety issues.

While no safety signals regarding MACEs or cancer emerged, other metabolic events, such as cholesterol increase, weight gain and menstrual alterations, were identified. These findings highlight that routine clinical practice represents a less controlled and more heterogeneous setting than randomized trials, underscoring the importance of continuous real-world safety monitoring to fully characterize treatment-associated risks.