NEW YORK (Reuters Health) – Patients with persistent oligoarticular juvenile idiopathic arthritis (JIA) are unexpectedly at high risk for growth retardation, Israeli researchers report in a May 30th on-line paper in the Journal of Pediatrics.

“JIA, the most common chronic rheumatic disease in children,” Dr. Shai Padeh, of Tel Aviv University, told Reuters Health by email, “may cause significant delay in growth either due to chronic inflammation or side effects from anti-rheumatic medications.”

“In comparison to patients with other subtypes of JIA,” he added, “patients with oligoarticular JIA — who have less than 5 affected joints — have milder disease requiring less medication, and are expected to grow well.”

The subtype, which reportedly accounts for about half of all JIA cases, is well controlled by corticosteroid injections into the joints at time of exacerbations.

To investigate the possible effect on growth, the researchers retrospectively reviewed data on 95 patients treated by these injections alone or in combination with disease-modifying antirheumatic drugs. Follow-up was for a mean of 6.0 years.

In assessing height growth in these patients, continued Dr. Padeh, “growth retardation was unexpectedly found in one third of the patients, including 11.6% with severe retardation.”

In patients receiving injections only, growth retardation overall was 30.6% and severe growth retardation was seen in 6.5%. Corresponding proportions in combination therapy patients were 44.4% and 21.2%.

The results were surprising, say the investigators, because “Previous reports have shown that growth retardation is common in other JIA subtypes but has been found in only 11% of patients with JIA with oligoarthritis.”

The team established that elevated erythrocyte sedimentation rate (ESR) values indicated a significantly higher risk for growth retardation. All other clinical variables had no association with growth retardation.

“Our hypothesis” to help mitigate such retardation, Dr. Padeh, observed “is that one should be more aggressive in treating those with elevated ESR.”

The researchers conclude that the findings warrant “future prospective studies in such areas as identifying additional risk factors over a longer period of time and until reaching final adult height.”

J Pediatr 2011.