MS4A4A was considered a marker of macrophages and has been associated with autoimmune conditions, such as rheumatoid arthritis (Mattiola et al., 2019), cutaneous systemic sclerosis (Rice et al., 2015), polyangiitis (Ishizu et al., 2013), and Kawasaki disease (Guo et al., 2020). Here, MS4A4A is linked to rheumatoid arthritis.