Aims Large synovial out-pouching is a rare complication in juvenile idiopathic arthritis (JIA). This case series aims to review the clinical presentation, differential diagnosis and investigation of this rare complication.
Methods Retrospective review of the clinical notes and diagnostic procedures of five patients with a diagnosis of JIA and large synovial out-pouching.
Results The authors reviewed the case notes of five patients with large synovial out-pouching from our cohort of patients with JIA. Three patients had a diagnosis of JIA systemic onset, one patient had JIA oligoarthritis and one patient had JIA undifferentiated arthritis. Two patients with systemic onset had large out-pouching from the hips. The 3rd patient with systemic onset had it from both hips, from both shoulders and from the ankle. The patient with oligoarthritis had it from the shoulder and the patient with undifferentiated arthritis had it from the knee. Other diagnoses in the patients were short stature, immunosupression, chronic anterior uveitis and diplegic cerebral palsy. Three patients presented with sudden non-tender swelling over the affected joint. One patient presented with pain of the affected joints. Another patient presented with restriction of movements of the affected joints. Three patients have had joint injections 1 to 4 months before the diagnosis of the large synovial out-pouching. All but one had a diagnostic MRI with gadolinium. One was diagnosed by USS. USS was the first imaging tool used but did not always help establish the diagnosis.
Conclusions Large synovial out-pouching may occur in any type of JIA. It tends to present suddenly and it is important to differentiate from other causes of sudden swelling. We have only described large synovial out-pouching in large joints. Previous joint injections may or may not be related to the appearance of the large out-pouching. MRI with gadolinium is the most accurate diagnostic investigation.