Objective To analyze the molecular genetic characteristics of a rare case of autosomal dominant spinal muscular atrophy-lower limb type 1 (SMALED1) family. MethodsRetrospective analysis of the clinical manifestations, laboratory examinations and genetic testing ina child and his family members diagnosed with SMALED1in the Rehabilitation Department of Nanjing Children"s Hospital in February, 2021. By literature review, we collect and summarize the genotype-phenotype associations of previously reported cases. Results The proband was a 2-year-old boy with mild global developmental delay, mainly motordevelopmental delay. The patient developed motor disorder after 1 year old, manifested as proximal muscular atrophy and weakness of both lower extremities, valgus feet, unstable standing alone, unable to walk alone, and duck gait in assisted walking. Physical examination showed his knee reflex disappeared; the electromyography showed spinal cord anterior horn,or root, cells lesions, and there was no significant abnormality in brain imaging. His mother and grandmother of the child had the same dyskinesia. Genetic tests identified a novelmissense mutation c.3326A>G (p.Y1109C) in the DYNC1H1 gene inthe affectedmemebers, andit was confirmedbeinginherited from his mother and grandmother. The site of SMALED1-associated in this study is consistent with previous studies, but it cannot explain the phenotype of mental development. Conclusion This study identified a novel mutation, which expanded the DYNC1H1 pathogenic variant spectrum. The proband with mental impairments confirms the lack of genotype-phenotype association of cortical dysplasias in previous studies, and it also shows that the phenotype associated with the novel variant p.Y1109C may be heterogeneous.