LACC1 and juvenile idiopathic arthritis: Despite LACC1/FAMIN mutations have been repeatedly identified in Mendelian forms of JIA, we failed to detect homozygous or compound heterozygous carriers of rare pathogenic LACC1 variants in the two groups of Spanish JIA patients analyzed, suggesting that mutations in LACC1 are not a major cause of JIA, and reinforcing the genetic complexity of this disorder.