Children with juvenile idiopathic arthritis (JIA) may experience impaired vertical growth in the first three years of the disease, according to researchers.

The study, “Growth patterns in early juvenile idiopathic arthritis: Results from the Childhood Arthritis Prospective Study (CAPS),” was published in the journal Seminars in Arthritis and Rheumatism.

Poor growth affects 1% to 17% of JIA patients and raises significant implications at both physical and psychosocial levels. Irreversible short stature and altered adult body structure are some of the consequences of the disease.

Several reasons have been reported to justify the poor growth in JIA patients, including the degree of general inflammation, use of corticosteroids (powerful anti-inflammatory drugs), and nutrition.

Recently, biologic therapies such as Enbrel (etanercept) and Actemra (tocilizumab) were shown to improve vertical growth in JIA patients. However, despite the intensification of treatment regimens and the evolution of biologic therapies, growth impairment persists in about 10% of patients.

Now, researchers investigated early growth patterns and factors associated with poor growth in a group of U.K. children. The study was conducted over the first three years following diagnosis, using data from the Childhood Arthritis Prospective Study (CAPS).

The study included 568 patients – 65% female, with a median age at time of diagnosis of 7.4 years – with a diagnosis of JIA and height measurements available at both baseline and three years after the study at follow-up.

Height was calculated as z-scores using World Health Organization growth standards for age and gender. Growth was assessed using changes in z-score and height velocity during the three-year period. The variation in height z-score was then used to identify possible factors associated with JIA.

Researchers found that height z-score decreased significantly during the study period, from -0.02 at baseline to -0.47 at three years follow-up.

Growth restriction, which implies a decrease in z-score of at least -0.5, was seen in 39% of the patients, with 22% showing moderately poor growth and 17% showing severe growth restriction.

The study also demonstrated that a lower baseline height z-score was the strongest predictor for improved growth.

“Patients with the lowest height z scores at presentation were also the most likely to see an improvement at 3 years,” the researchers wrote.

The total time of oral or intravenous steroid treatment was found to be associated with decreased height z-score from baseline to three years.

“Although overall height at 3 years after initial presentation to rheumatology is within the population norm, as a cohort, children with JIA experience a reduction of growth in height over the first 3 years of disease,” researchers wrote.

“Continued follow-up of these children into adolescence will indicate if these early losses in vertical growth can be reversed prior to reaching final adult height,” they added.