Abstract: 【Abstract】 Objective To evaluate the diagnostic and differential diagnostic value of reflectance confocal microscopy （RCM） for cutaneous lupus erythematosus （CLE）. Methods A total of 169 patients with clinically suspected CLE were retrospectively enrolled from the Department of Dermatology, the Third Xiangya Hospital of Central South University between January 2020 and December 2025. All patients underwent both RCM and histopathological examinations. Using histopathological findings as the gold standard, the sensitivity, specificity, and accuracy of RCM for diagnosing CLE were calculated. The RCM features of discoid lupus erythematosus （DLE）, subacute CLE （SCLE）, and acute CLE （ACLE） were summarized, and key features differentiating CLE from lichen planus, actinic keratosis, granuloma annulare, dermatomyositis, psoriasis, and seborrheic dermatitis were analyzed. Results Among the 169 patients with clinically suspected CLE, 84 （49.7%） were pathologically confirmed; 75 （44.4%） were diagnosed with CLE by RCM, of whom 68 showed concordance between RCM and histopathological diagnosis. The sensitivity, specificity, and accuracy of RCM for diagnosing CLE were 80.95% （95% CI: 71.70% - 88.00%）, 91.76% （95% CI: 83.80% - 96.30%）, and 86.39% （95% CI: 81.20% - 91.60%）, respectively, with a kappa coefficient of 0.73 （95% CI: 0.58 - 0.87）. The core RCM features distinguishing CLE from other diseases included the indistinct dermo-epidermal junction, liquefaction degeneration of the basal cell layer, and perivascular or perifollicular inflammatory infiltration in the superficial dermis. In addition, RCM revealed that DLE was characterized by hyperkeratosis, follicular plugging, and prominent infiltration of melanophages and inflammatory cells around dermal vessels and hair follicles; SCLE was characterized by epidermal atrophy and thinning, dermal vascular dilatation and congestion, and marked perivascular inflammatory infiltration; ACLE was characterized by follicular plugging, superficial dermal edema, dermal vascular dilatation and congestion, and perivascular inflammatory infiltration. Conclusion RCM demonstrated favorable diagnostic performance for CLE, could provide imaging clues for the diagnosis of common CLE subtypes and their differentiation from mimicking conditions, and may serve as a valuable adjunctive tool in the clinical diagnosis of CLE.

Key words: Lupus erythematosus, cutaneous, Reflectance confocal microscopy, Lupus erythematosus, discoid, Diagnosis, Differential diagnosis