In our study, we investigated, for the first time, the synovial histological features of a selected cohort of PsA patients, with peripheral joint involvement, compared to ACPA/RF seronegative RA cohort stratified based on the disease phase (disease onset and after DMARD insufficient response respectively) finding differential histological features of synovial tissue inflammation composition and biomarkers of therapeutic response. The gene discussed is PRTN3; the disease is rheumatoid arthritis.