The first case of association of s-JIA and FHL-related genes was reported by Hazen et al. in 2008, who described an 8-year-old girl with s-JIA and hemophagocytosis, without complete criteria of MAS, who was found to have compound heterozygous mutations of UNC13D and reduced NK cell cytotoxic function (135). Here, UNC13D is linked to juvenile idiopathic arthritis.