PRPS1L1 and rheumatoid arthritis: The strongest signals of association outside of the MHC (p < 10-4) occurred with FRY (furry homolog), PRPS1L1 (phosphoribosyl pyrophosphate synthetase 1-like 1), and ARNTL (ARNT-like protein 1, brain and muscle), each containing accumulations of rare variants that appear to be protective for RA (Table 1).