A patient carrying a heterozygous p.Asn267Ser TARDBP missense mutation diagnosed as ALS and only involving lower motor neurons.

Amyotrophic lateral sclerosis (ALS) is a rare neurodegenerative disease involving upper motor neurons (UMN) and lower motor neurons (LMN), which can be caused by mutations of pathogenic genes such as superoxide dismutase 1 (SOD1), sarcoma fusion (FUS), and TAR-DNA binding protein (TARBDP/TDP-43). Among these pathogenic genes, TARBDP mutation accounts for approximately 1% of sporadic ALS (sALS). The clinical phenotype of ALS is heterogeneous owing to different mutant genes and sites. Here, we report a case of sALS from China, the pathogenic site (c.800A > G) of TARDBP in this patient was identified by whole-exome sequencing. But his clinical symptoms involve only the LMN, presented with progressive limb weakness, and dyspnea, without obvious limb muscle atrophy. We considered this patient as a possible LMN-dominant ALS variant and this report further explores the genotype-phenotype correlations of ALS10. Furthermore, interestingly, the pathogenic site in this person was previously reported in a Parkinson's disease (PD) patient and frontotemporal dementia (FTD) patient. Our findings illustrate the clinical heterogeneity and the types of diseases which carry p.Asn267Ser TDP-43 mutation were broadened furtherly. Meanwhile, considering that the range of neurodegenerative diseases associated with this mutant site may be expanding, the mechanism of different neurodegenerative changes mediated by the same pathogenic site still needs to be further studied.