reported that a child suffering from JIA had compound heterozygous mutations in UNC13D; one allele contained a known mutation in the splice donor site of intron 9 (753 + 3 [G>A]), whereas the other allele carried a novel missense mutation in exon 18 (1579 [C>T] R527W), which reduced the cytotoxic function of NK cells. The gene discussed is UNC13D; the disease is juvenile idiopathic arthritis.