Height change in children with juvenile idiopathic arthritis after two years of etanercept (Enbrel).

What is it about?

Juvenile idiopathic arthritis (JIA) affects approximately 1 in 1000 children in the UK, with disease often continuing into adulthood. Children with JIA can experience delayed and restricted growth, with up to 17% of children with JIA having short stature. There may be multiple reasons for this poor growth including inflammation caused by the arthritis and the use of steroids. In 2002, a biologic therapy etanercept was licensed in Europe for use in JIA. Short-term clinical trials showed etanercept to be effective in improving disease severity, reducing disease flares and improving disability and quality of life. It is possible that one further benefit of etanercept may be an improvement in growth if started before the child reaches full adult height. A large study in the USA showed height increased after 3 years in patients treated with both etanercept and methotrexate. Little is known about what may influence height improvement on etanercept treatment, and in particular the relationship of height with control of disease. A total of 191 children with JIA treated with etanercept were included in this analysis. Patients were more commonly female (65%), with an average age of 11 years old at the start of etanercept treatment. More than half the patients were on methotrexate (58%) and 38% were on steroids at the same time as their etanercept treatment. Overall, disease activity of the patients improved after 2 years of treatment with etanercept. At the start of treatment with etanercept, the children in this study were much shorter compared with what they should have been based on their age and gender. After 2 years of treatment with etanercept, the height of these children improved significantly. However, despite this, height at 2 years remained lower than what would have been expected based on their age and gender. Patients with systemic arthritis remained the shortest of all patients even after 2 years of etanercept treatment. Children who were much shorter than they should have been at start of treatment seemed to improve in height better over 2 years of etanercept treatment and children who were not on steroids at start of etanercept also improved in height more.

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Why is it important?

This study was in a real-world group of children with severe JIA in the UK and represents some of the first children in the UK to have received etanercept treatment after it was initially approved. It was found that the height of these children improved over 2 years of treatment on etanercept suggesting that the control of the inflammation in arthritis may help growth in some children. The results of this study may provide reassurance to children with severe JIA treated with etanercept. Whilst they may have been initially shorter than they should have been before starting therapy, perhaps due to the inflammation of under-controlled disease, after 2 years of treatment they should significantly improve in growth.

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