Isolated inflammatory coxitis associated with protrusio acetabuli: a new form of juvenile idiopathic arthritis?

Background. Isolated hip disease in the context of chronic childhood inflammatory arthritis is uncommon. This paper reports 14 children who presented to the rheumatology and orthopaedic departments of our hospitals with severe hip symptoms, and who continued to have primarily hip disease throughout their clinical course. Our aim was to characterize and present the relevant demographic, clinical, investigational, treatment and outcome data from the above cohort. Methods. All paediatric cases with the diagnosis of protrusio acetabuli, Otto pelvis or idiopathic chondrolysis who were seen in the past 15 yr at Great Ormond Hospital and Middlesex Hospital in London were identified and their case notes were searched retrospectively for relevant information. Results. In 11 cases, the disease progressed to involve no joints other than the contralateral hip. None were considered to have a specific subtype of juvenile idiopathic arthritis (JIA) and all tested were negative for HLA-B27. Elevation of serum inflammatory markers was variable. Protrusio acetabuli was the predominant radiological feature. There were definite inflammatory changes on the gadolinium-enhanced magnetic resonance imaging study in all patients who had this procedure performed (seven cases). Microbiological investigations were all consistently negative. Severe hip disease resulted in considerable ongoing symptoms and disability. Six cases were treated with disease-modifying anti-rheumatic drugs. Total hip replacement has been required in four patients to date, with major functional improvement. Conclusions. These cases represent severe and disabling primary hip disease with considerable clinical and investigational inflammatory features. Such a mode of presentation has not been described previously in the context of childhood chronic inflammatory arthritides, and may represent a separate oligoarthritis subtype of JIA.