Genetic variations in NOD1/CARD4 and/or NOD2/CARD15 have previously been identified in many diseases such as inflammatory bowel disease [20,46], Crohn’s disease [22,24], sarcoidosis [23], non-Hodgkin lymphoma [21], cancer [16,26,27] and RA [55]. Here, NOD1 is linked to rheumatoid arthritis.