UNIQUE MONOARTHRITIS PRESENTATIONS IN OLIGOARTICULAR JUVENILE IDIOPATHIC ARTHRITIS: A CASE SERIES

Abstract

Abstract BACKGROUND: Juvenile idiopathic arthritis (JIA) is a heterogeneous group of seven immune-mediated chronic inflammatory diseases that target the joints in children younger than 16 years of age. In Canada and worldwide, the estimated prevalence of JIA is approximately 1 per 1,000 children. Almost half of JIA patients are diagnosed with oligoarticular juvenile idiopathic arthritis (oligoJIA). OligoJIA, the most common chronic inflammatory arthritis of childhood, usually affects the knees and ankles. OligoJIA monoarthritis presenting with atypical, severe joint involvement is exceedingly rare and may have poor prognosis. OBJECTIVES: To identify the cases of children that presented with atypical monoarthritis and were diagnosed with oligoJIA in our Pediatric Rheumatology Clinic. Our aim is to describe their demographic, clinical, laboratory, and imaging features. In addition, we reviewed ten similar cases published in the literature. DESIGN/METHODS: This is a retrospective case series study. Fifty-three children with JIA from our inception cohort established in September 2015 were screened for the study. Other JIA subtypes and oligoJIA with ≥ 2 joints affected were excluded. RESULTS: Twenty-five out of 53 (47%) children with JIA were diagnosed with oligoJIA. Four of these 25 children (16%) presented with atypical monoarthritis of the hip, wrist or elbow. None had uveitis. All four were girls with a median age of 11.5 ± 3.5 years (range 9-16 years). Median duration of symptoms prior to diagnosis was 9.5 months. Median follow-up was 5.5 ± 3.5 months. All four patients had normal inflammatory markers. Two children were HLA-B27 positive and had hip arthritis. Three out of four (75%) children had second degree relatives with rheumatologic diseases. Three children (75%) diagnosed with hip, wrist and elbow arthritis respectively had cartilage loss and significant bone changes at presentation, including erosions.Only 10 cases of oligoJIA presenting with atypical monoarthritis have been published to date: 7 children with wrist involvement and 3 others with elbow arthritis. Five out of 7 (71%) children presenting with wrist oligoJIA had bone damage, whereas none of those with elbow arthritis had bone changes at presentation. CONCLUSION: Hip, wrist and elbow oligoJIA can have an aggressive course and present with bone damage. Prompt diagnosis is essential in avoiding irreversible bone and joint damage. Early referral to specialized care can improve their diagnosis, treatment and outcome.