Biologics promote catch-up growth in young Juvenile idiopathic arthritis patients with lower body height.

Background: Juvenile idiopathic arthritis (JIA) is accompanied by growth retardation especially in severe cases. While the use of biologics has shown efficacy in restoring growth impairment, data from Asia are limited. We aim to investigate the growth of JIA patients and identify those who can benefit from the use of biologics in Taiwan.

Methods: JIA patients who received regular follow-up and treatment at a tertiary medical center in Taiwan between January 2011 and June 2023 were retrospectively reviewed. General demographics and growth parameters, including body height, body weight, and body mass index (BMI), were collected at the time of biologics initiation, then at 6 and 12 months into treatment and they were transformed into z-scores for further analysis.

Results: A total of 104 JIA patients, including 52 biologics-free controls, were enrolled. Enthesitis-related arthritis (ERA) accounted for 51% all cases. The initial z-scores for body height, body weight and BMI were -0.33, -0.35, -0.45, respectively. A significantly higher proportion of biologics-treated patients achieved catch-up growth, defined as a continuous increase in height z-scores 1 year following biologics treatment, compared to the biologics-free controls (38% vs. 12%; p = 0.002) 12 months into treatment. In subgroup analysis, JIA patients with lower initial z-scores for height (p = 0.021), a shorter period between symptom onset and diagnosis (p = 0.026), younger ages at the time of biologics initiation (p < 0.001) and higher accumulative dose of steroid before biologics (p = 0.048) are more likely to achieve catch-up growth. Combining the age at the time of biologics initiation and patients' initial z-score for height may be sufficient to predict catch-up growth following treatment with biologics (AUC = 0.804; p < 0.0001).

Conclusions: Growth retardation appears limited among JIA patients in Taiwan. Initiation of biologics at a younger age may improve linear growth, especially for patients initially shorter for their age.