An Autopsy Case of <scp>ALS</scp> Which Clinically Presented Sporadic Adult‐Onset Lower Motor Neuron Disease and Genetically Had p. <scp>Leu127Ser</scp> ( <scp>L126S</scp> ) Variant in <scp> <i>SOD1</i> </scp> and <scp> <i>SMN2</i> </scp> Deletion

Herein, we report an autopsy case of sporadic amyotrophic lateral sclerosis (ALS) with a p. L127S (L126S) SOD1 variant, SMN2 deletion and one hybrid SMN. A 43-year-old Japanese man noticed muscle weakness in his left lower extremity. At the age of 51, his muscle strength was moderately diminished in the upper extremities and severely in the lower extremities with hyporeflexia. At the age of 55, he started noninvasive intermittent ventilation (NIV) during nighttime. At the age of 57, he developed dysphagia and died of pneumonia. The total clinical course was 14 years and 8 months (13 years 9 months until NIV). Pathologically we found severe loss of lower motor neurons, moderate neuronal loss in Clarke's nuclei and mild grumose degeneration of the dentate nucleus. The primary motor cortex was well preserved and the pyramidal tracts showed vague myelin pallor in the lumbar cord. There were a few conglomerate hyaline inclusions (CHIs) that were negative for Bodian staining. Immunohistochemically, CHIs were positive for phosphorylated neurofilament (pNF) and were stained with Uq and SOD1 to varying degrees. Some CHIs contained granular-like components positive for p62. A post-mortem genetic test revealed that the patient had 2 copies of SMN1, 0 copies of SMN2, and one hybrid gene with exon 1 to 7 of SMN2 and SMN1 exon 8. Additional gene research elucidated a heterozygous SOD1 p. Leu127Ser (L126S) mutation. Compared to previous reports of ALS with the same mutation, the distribution of degenerative lesions was similar. It has been suggested that SMN2 deletion may not be directly implicated in lower motor neuron pathology, but further research is needed to confirm this. Further accumulation of cases is necessary to determine the effect of SMN2 on SOD1-ALS.