Prospective reflectance confocal microscopy monitoring in dupilumab-treated atopic dermatitis.

BACKGROUND: Dupilumab provides substantial clinical benefit in moderate-to-severe atopic dermatitis, but whether clinical improvement is accompanied by microstructural resolution on reflectance confocal microscopy (RCM) remains unclear. OBJECTIVES: To describe baseline clinical and RCM findings, evaluate longitudinal clinical and microstructural changes and explore associations between baseline RCM features and week 24 outcomes. METHODS: We conducted a prospective real-world cohort study at a tertiary academic hospital in Buenos Aires, Argentina. Consecutive paediatric and adult patients aged ≥6 months with moderate-to-severe atopic dermatitis initiating dupilumab were assessed at baseline, week 12 and week 24. Clinician-reported outcomes, patient-reported outcomes and prespecified binary RCM features were summarized at each visit. Paired baseline-to-week 24 analyses assessed within-patient clinical changes and RCM feature transitions. Associations between baseline RCM findings and week 24 outcomes were explored using Fisher's exact tests and linear regression models. RESULTS: Thirty-seven patients were included; 19 (51.4%) were paediatric and 25 (67.6%) were male. Baseline disease burden was high, with median EASI 28.0 (IQR 19.0-33.0). Baseline RCM showed epidermal disorganization, spongiosis and dilated vessels in all patients, with dermo-epidermal junction inflammation in 34/37 (91.9%). In paired baseline-to-week 24 analyses, median EASI decreased from 28 (IQR 18-32) to 2 (IQR 1-6), with a median individual improvement of 22 points; EASI-75 was achieved by 76.2%. Several baseline-positive confocal features resolved by week 24, including acanthosis (81.8%), hyperkeratosis (72.7%), parakeratosis (66.7%) and epidermal inflammation/exocytosis (64.7%). However, epidermal disorganization, spongiosis and dilated vessels remained frequent, including among EASI-75 responders. CONCLUSIONS: Persistent RCM abnormalities, particularly epidermal disorganization, spongiosis and dilated vessels, were observed at week 24, even among EASI-75 responders. These findings suggest that clinical response to dupilumab may not always coincide with complete microstructural normalization and that RCM may provide complementary information beyond clinical outcomes.