Clinical efficacy and safety of intravenous ferric carboxymaltose treatment for restless legs symptoms and low serum ferritin in children with autism spectrum disorder

Abstract

Background: Restless legs syndrome (RLS) may be underdiagnosed in children with autism spectrum disorder (ASD) due to difficulty expressing the symptoms in their own words. In addition, administration of oral iron may be particularly difficult in children with ASD.

Methods: This was a retrospective, open-label case series of children with ASD, restless legs (RL) symptoms, and serum ferritin <30 μg/L, who either had failed or did not tolerate oral iron, and were subsequently treated with intravenous (IV) ferric carboxymaltose (FCM). Patients received a single dose of IV FCM, 15 mg/kg up to a maximum dose of 750 mg. Data collected pre- and eight weeks post-infusion included presenting symptoms, serum ferritin, iron profile, and Clinical Global Impression Scale (CGI-Severity pre- and CGI-Improvement post-infusion). Adverse effects were assessed.

Results: Nineteen children, 4-11 years old (12 male, median age 6, interquartile range (IQR 4-11) were included. A definite RLS diagnosis was identified in 6 verbal children (31.6%). RL symptoms (designated probable RLS) in the 13 other children met all RLS diagnostic criteria except "improvement of symptoms with movement," which was not definitively determined. Baseline median values were: ferritin 10 μg/L (IQR 10-16), iron 66.5 μg/dL (IQR 57-96), TIBC 382 μg/dL (IQR 360-411) and transferrin saturation 19% (IQR 14-28). Median CGI-S was 4 (moderate symptoms) (IQR 3-4). At eight weeks after IV FCM, all measures were improved. Median ferritin was 68 μg/L (IQR 62.5-109, p < 0.00045). Median CGI-I was 1 (very much improved) (IQR 1-2). All children meeting definite RLS criteria improved. Three children in the probable RLS group did not improve. Children meeting the full RLS criteria had lower baseline ferritin levels than those with a probable diagnosis (9 μg/L, IQR 9-10 vs. 13 μg/L, IQR 10-16, Mann-Whitney test p < 0.045). Adverse effects included lightheadedness, gastrointestinal discomfort, fever, and headache among others.

Conclusions: The majority of children (84.2%) with ASD, restless legs symptoms, and serum ferritin <30 μg/L had clinical improvement and significantly better serum iron parameters after a single IV FCM infusion. Although larger, randomized trials are needed, IV FCM appears to be a promising treatment for this subset of children with ASD.

Keywords: Autism spectrum disorder; Children; Ferric carboxymaltose; Ferritin; Iron supplementation; Restless legs syndrome.