LEPROTL1 and rheumatoid arthritis: In support of their relevance, all genes/rules characterizing ‘CG’ were significantly overexpressed in CG as compared with both RA and OA (Additional file 5) – with the exception of the gene/rule LEPROTL1 (leptin receptor overlapping transcript 1), which also showed significant differences, but with an opposite orientation (all P ≤ 0.05; Mann Whitney U test).