One hypothesis states that these MBL2 gene variants result in susceptibility to various infectious and autoimmune diseases, such as rheumatoid arthritis [2], Kawasaki disease [3,4], recurrent vulvovaginal candidiasis [5], respiratory distress syndrome in preterm infants [6], hepatitis B infection [7], severe acute respiratory syndrome coronavirus infection [8], etc. However, whether these MBL2 gene variants are really associated with susceptibility to various diseases remains unknown and controversial. The gene discussed is MBL2; the disease is rheumatoid arthritis.