Differences among Indian and European pemphigus patients based on demographics, clinical parameters and propensity for relapse: results of a prospective bicontinental cohort study.

Limited studies have explored pemphigus variations among different ethnic groups residing in their respective geographical locations. This bicontinental study aimed to compare clinical and immunological parameters in Indian and European pemphigus patients in complete remission, off therapy, or on minimal therapy. 105 patients (India, n= 75; Bulgaria, n=15; Greece, n=15) with pemphigus vulgaris (PV) or pemphigus foliaceous (PF) in complete remission on minimal therapy (n=64) or complete remission off therapy (n=41) were recruited. Demographic, clinical, and immunological parameters were compared. Indian patients were significantly younger, the maximal disease severity during the preceding active disease phase was significantly lower, and treatment duration until complete remission was significantly shorter, compared to European patients. European patients had significantly higher anti-Dsg3 serum levels and higher IgG positivity rate based on direct immunofluorescence microscopy at baseline. Furthermore, European patients revealed higher CD19, CD19+ CD27+ cell counts, compared with patients from India. Of note, none of the European patients (n=30) relapsed within the study period, in contrast to 29/75 (38.6%) Indian patients. Treatment strategies differed significantly between the two cohorts, with more frequent utilization of rituximab to achieve remission in the Indian cohort, while prednisolone was more widely used for maintaining remission in the European cohort. The observed heterogeneity of pemphigus among patients of different ethnicities in terms of demographics, clinical parameters, and propensity for relapse may be due to genetic background or different treatment strategies.