Juvenile idiopathic arthritis is the most prevalent rheumatic disease in children. The systemic form accounts for 10-15% of cases and is characterized by a dysregulation of the innate immune system. The prognosis of the disease is related to systemic involvement and complications such Macrophagic activation síndrome (MAS) and to the extent and severity of arthritis. The introduction of new drugs has changed the prognosis of these patients but continues to be a diagnostic and therapeutic challenge. This study presents the clinical and paraclinical characteristics of a cohort of Colombian patients with sJIA

Methods: Descriptive retrospective study of a cohort of patients from 1996 to 2016. Analysis of clinical records of patients with a definitive diagnosis of systemic juvenile idiopathic arthritis in 2 pediatric rheumatology clinics in Bogota,Colombia

Results: n=69. Mean age at diagnosis 6.7 years (SD 3,9 years), sex ratio F:M 1,37:1. The mean follow up time was 102 months (10-1080 months). Two patients (3%) died during follow up. Causes of death were MAS in one patient and multiple organ failure following gastrointestinal infection in the other. At diagnosis all patients present fever with a mean duration of 41 days (16-180 days). Rash was present in 93%, arthritis in 86% being polyarticular in most of the patients (56%), organomegaly in 50%, adenomegalies in 22% and serositis in 20% of patients. Laboratory features showed leukocytosis in 96%, anemia in 91% and thrombocytosis in 83% of patients. Increased levels of transaminases, ferritin, globular sedimentation velocity and C reactive protein were present in 19%, 97% and 100% (both) respectively. 48% patients had polyarticular course of arthritis and 44% systemic involvement. MAS occurred in 4 patients (6%) during debut and course of the disease. Regarding treatment, most of the patients were prescribed with nonsteroidal anti-inflammatory drugs (97%) and steroids (84%). Seven percent received Cyclosporine, 72,5% Methotrexate and 23% required biological treatment. At the last follow up 70% of patients were in functional class 1 or 2 and 7% were in class 4. There was a significant association between early disease onset (1-5 years) and functional class 3 and 4 (p=0,014). Also the worst functional class correlated with a polyarticular course (p=0,010). Patients with polyarthritis at onset had a worst functional class at the last follow up (p=0,003) and had a higher risk of continuing with polyarthritis at course of disease (p=0,000). Polyarticular course was more frequent in girls (p=0,016). Organomegalies at onset were more frequent in patients with a polyarticular course (p=0,007)

Conclusion: sJIA is a severe disease. Early onset and polyarticular involvement are prognostic markers. Aggressive treatment and periodic monitoring of complications may improve the prognosis of these patients