Results from the PRAIRI (prevention of clinically manifest RA by B cell directed therapy in the earliest phase of disease) study has shown that a single infusion of rituximab in patients who were seropositive (positive for rheumatoid factor (RF) or anti-citrullinated protein antibodies (ACPA)) but without clinical synovitis can delay onset of arthritis, though not prevent it [3]. This evidence concerns the gene PRTN3 and Arthritis.