To define the clinical manifestations, determine prevalence, and heighten awareness about the arthropathy of Down syndrome.

Using diagnostic codes for Down syndrome and juvenile idiopathic arthritis (JIA), we identified 9 cases in our hospital system. Each case met diagnostic criteria for JIA. Cases were compared with 21 additional literature cases. Prevalence was determined with diagnostic codes.

Average delay from symptom onset to diagnosis was 2 years. Age at onset varied from 20 months to 12 years. Sex distribution was equal. At symptom onset, 57% had polyarticular disease, and 43% had oligoarticular disease, but 54% with oligoarticular disease progressed to polyarticular disease. Seventy-two percent had an elevated erythrocyte sedimentation rate. Most required second-line therapy, and almost half had development of joint subluxation. Prevalence of Down syndrome arthropathy is 8.7/1000, more than 6 times higher than JIA in the general population.

The arthropathy of Down syndrome is an underrecognized condition that results in chronic disability and functional impairment in a population already at significant risk. Children with Down syndrome are predisposed to autoimmune disorders, but arthritis is overlooked in surveillance guidelines. To maximize joint function and quality of life, providers caring for children with Down syndrome need a high index of suspicion for the related arthropathy.