Association of red cell distribution width with disease activity and antidesmoglein antibody levels in pemphigus vulgaris: a prospective case–control study

Background Pemphigus vulgaris (PV) is a severe autoimmune blistering disease that requires reliable monitoring biomarkers. Red cell distribution width (RDW) and mean platelet volume (MPV) have emerged as potential nonspecific inflammatory markers in various systemic diseases, but their clinical utility in PV is unclear. Objectives To evaluate the association between RDW, MPV, clinical disease activity [Pemphigus Disease Area Index (PDAI)] and serological markers [antidesmoglein (anti-Dsg) 1 and 3 antibodies] in patients with PV, and to assess their longitudinal changes following systemic treatment. Methods This prospective case–control study included 68 patients with PV and 68 age- and sex-matched healthy controls. In the patient group, PDAI scores, anti-Dsg titres (enzyme-linked immunosorbent assay), RDW and MPV were assessed at baseline and 3 months after initiating standard treatment. Due to the non-normal distribution of data (confirmed by the Shapiro–Wilk test), nonparametric tests including Mann–Whitney U, Wilcoxon signed-rank and Spearman’s rank correlation (ρ) were used. Continuous variables are reported as median (interquartile range). Results Baseline RDW levels were significantly higher in patients with PV compared with control participants [13.9% (interquartile range 13.3–14.7) vs. 13.5% (interquartile range 12.9–15); P = 0.05]. Baseline RDW showed significant moderate positive correlations with PDAI (ρ = 0.50, P < 0.001), anti-Dsg1 (ρ = 0.60, P < 0.001) and anti-Dsg3 antibodies (ρ = 0.55, P < 0.001). Following 3 months of treatment, despite significant clinical and serological improvement (P < 0.001), RDW and MPV values did not show significant changes (P > 0.05). MPV levels did not differ significantly between patients and controls at baseline. A ceiling effect was observed for baseline anti-Dsg3 levels. Conclusions RDW is elevated in patients with PV and correlates with clinical and serological markers of disease activity, suggesting that it reflects the systemic inflammatory burden. However, RDW may not be a sensitive marker for tracking short-term therapeutic responses. Further longitudinal studies are needed to determine the role of RDW as an adjunctive monitoring tool in the management of chronic PV.