When investigating IgG and ACPA Fc sialylation as well as bone structure in autoantibody-positive healthy individuals before the onset of rheumatoid arthritis, we again found that bone volume and trabecular numbers are significantly lower in individuals with low IgG and low ACPA sialylation compared with those with a high-sialylation status (Supplementary Fig. 5). The gene discussed is PRTN3; the disease is rheumatoid arthritis.