Clinical characteristics of children affected by autism spectrum disorder with and without generalized hypotonia

In this cross-sectional study, we aimed to evaluate the association between generalized hypotonia (GH) and demographic features and clinical characteristics in toddlers (2 to 5 years) with autism spectrum disorder (ASD). Among 93 children, 32 (34.4%) had GH. These patients had a later onset of independent walking (17 vs. 15 months, p < 0.01), a higher proportion of motor stereotypies (65.6 vs. 27.9%, p < 0.01), a lower mean total score in the parental-reported Generic Core Scale of Pediatric Quality of Life Inventory 4.0 (71 vs. 76 points, p 0.03), and a higher mean total score in the Calibrated Severity Score of Autism Diagnostic Observation Schedule version 2 at diagnosis (6 vs. 5 points, p 0.02) compared to the group without GH.Conclusion: Hypotonia is associated with other motor abnormalities and could be an early marker for higher autistic symptom severity and lower quality of life in young children with ASD. What is Known: • Motor function is closely related to autism spectrum disorder (ASD) • Muscle hypotonia is present in 15% to 67% of children with ASD What is New: • Muscle hypotonia is associated with higher autistic symptom severity and lower quality of life in children with ASD • Children with ASD and muscle hypotonia have more commonly motor stereotypies and a later onset of independent walking.