From OMIM
The James type of infantile spinal muscular atrophy (SMAJI) is a severe neuromuscular disorder with onset of hypotonia in the first weeks or months of life. Some patients may have normal early motor development prior to the onset of symptoms, but all show delayed motor milestones with loss of previous motor skills in the first year of life. There is muscle weakness and atrophy, primarily affecting distal muscles, resulting in the inability to walk independently and causing impairment of fine motor skills of the hands. The disorder is slowly progressive: additional features may include feeding difficulties with failure to thrive, foot deformities, hyperlordosis, scoliosis, vocal cord weakness, and respiratory insufficiency, which may require intervention. Laboratory studies are most consistent with a motor neuronopathy, although skeletal muscle biopsy may also show myopathic features. This disorder is considered to be at the most severe end of the phenotypic spectrum of disorders caused by mutations in the GARS1 gene. The disorder is phenotypically similar to SMA1 (253300) (summary by Eskuri et al., 2012; Markovitz et al., 2020).  http://www.omim.org/entry/619042