SPTLC1 and amyotrophic lateral sclerosis: However, recent evidence has suggested that mutations in SPTLC1 are linked to motor phenotypes including juvenile ALS.34 Interestingly, atypical phenotype of growth retardation, hypotonia, and vocal cord paralysis was reported in a patient with the p.Ser331Phe mutation in SPTLC1, which is close to the p. Ser340Leu variant identified in this study.35