An autopsy report of a long‐survival case of familial amyotrophic lateral sclerosis with <scp>SOD1 G93S</scp> gene mutation: Lack of <scp>SOD1</scp>‐positive inclusion in the remaining neurons

We describe the case of a 70-year-old Japanese man with familial amyotrophic lateral sclerosis (fALS) associated with a p.Gly93Ser mutation in the copper/zinc superoxide dismutase (SOD1) gene. This mutation is one of the relatively rare SOD1 mutations, with only one previous autopsy report, and is known for its longer disease duration. As previously reported, the patient had weakness in the lower limbs at age 33, followed by dysphagia, dysesthesia in the lower limbs, and autonomic dysfunction. He required mechanical ventilation at age 44 and died of acute pancreatitis at age 70. Neuropathologically, multisystem degeneration was observed beyond lesions typical of familial ALS with posterior column involvement. In addition, there was no SOD1-positive inclusion in the remaining motor neurons. The absence of SOD1-positive inclusion is a rare feature observed predominantly in long survival cases with SOD1 gene mutations. We hypothesize that the considerably lower amount of abnormal SOD1 protein in the motor neuron cells might explain our patient's extraordinarily long clinical course.