Elbow monoarthritis: an atypical onset of juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is the most common chronic rheumatic condition in childhood and an important cause of short and long term disability. Oligoarthritis is defined as an arthritis that affects four o fewer joints during the first 6 months of disease. The large majority of patients within this category belongs to a quite well defined disease which is not observed in adults. It is characterized by an early onset (before 6 years of age), an asymmetric arthritis involving mainly large joints, a female predilection, a high frequency of positive antinuclear antibodies (ANA), a high risk for developing chronic iridocyclitis and consistent HLA associations. We describe 3 clinical cases who presented monoarthritis of the elbow as early sign of oligoarticular JIA. All patients showed inflammatory markers elevation and 2/3 were ANA positive. MRI showed the presence of synovial inflammation without bone involvement. Intraarticular triamcinolone hexacetonide, led to remission in one case, while in the other two there was a re-activation of the disease treated with NSAIDs and/or MTX. The reported cases represent 0.6% of 490 patients with JIA followed by our unit in the last 10 years. Cases of exclusive involvement of the elbow at onset of JIA in literature are rare. Therefore, we report 3 cases of monoarthritis of the elbow as initial sign of oligoarticular JIA, a very atypical onset of this disease.