LEP and obesity due to melanocortin 4 receptor deficiency: Recent studies have suggested obesity should be considered a confounding factor for RA and PsA disease severity and progression [27, 28], therefore, we stratified patients into high BMI (> 25) and low BMI (< 25) (Supplementary Fig. 1C), and observed that selective metabolic markers were higher in the RA BMI high group, including Leptin (p < 0.01) and c-Peptide (p = 0.08).