Proband B.III.1 is a now-13-year-old female who presented at age 3 with an unusual confluence of inflammatory arthritis (extended oligoarticular juvenile idiopathic arthritis), a neuroinflammatory movement disorder, and cutaneous tumid and chillblain lupus rashes and was later found to have elevated blood monocyte CD169 expression suggestive of high serum type I IFN activity (Biesen et al., 2008; Sakumura et al., 2023; York et al., 2007). Here, SIGLEC1 is linked to extended oligoarticular juvenile idiopathic arthritis.