Interferon-α biological activity is associated with disease activity and risk of flare in cutaneous lupus erythematosus: A monocentric study of 184 patients

Background: Cutaneous lupus erythematosus (CLE) is associated with unpredictable flares and may induce permanent damage. There is currently no biomarker routinely available in CLE. Objective: To evaluate the performance of interferon-a (IFN-a) biological activity as biomarker of CLE activity and risk of flare. Methods: Cohort study including consecutive CLE patients with or without associated systemic lupus erythematosus. Serum IFN-a biological activity (IU/mL) was determined by assessing the antiviral protection afforded by patients' serum. Results: At first sampling, among 184 included patients, the prevalence of positive IFN-a activity ($2 IU/ mL) was 38%. Positive IFN-a activity was associated with active CLE (odds ratio = 3.11 [95% CI: 1.61-6.01], P = .006), moderate-to-severe CLE activity (odds ratio = 4.43 [95% CI: 1.99-9.86], P = .001) and associated systemic lupus erythematosus (odds ratio = 2.17 [95% CI: 1.19-4.00], P = .01). Among 65 patients with inactive CLE, the risk of CLE flare at 6 months was significantly higher among patients with positive vs undetectable IFN-a activity (hazard ratio 4.95 [95% CI: 1.12-21.78], P = .03). No association was found with anti-double-stranded DNA antibodies and low complement levels. Limitations: IFN-a activity is not universally available. Conclusion: IFN-a activity is associated with cutaneous activity and prognosis in CLE and can be used to predict CLE flares in clinical practice. ( J Am Acad Dermatol 2025;92:1039-48.)