Amyotrophic lateral sclerosis (ALS) with the mutations in the fused insarcoma/translocated in liposarcoma gene

Amyotrophic lateral sclerosis (ALS) is an adult onset neurodegenerative disorder characterized by the death of upper and lower motor neurons. Mutations in the fused in sarcoma/translated in liposarcoma (FUS/TLS) gene have been discovered to be associated with familial ALS. In a Japanese family with familial ALS, we found the R521C FUS/TLS mutation, which has been reported to be found in various ethnic backgrounds. The family history revealed 23 patients with ALS among 46 family members, suggesting a 100% penetrance rate. They developed muscle weakness at an average age of 35.3 years, and the average age of death was 37.2 years. Neuropathological examination revealed remarkable atrophy of the brainstem tegmentum characterized by cytoplasmic basophilic inclusion bodies in the neurons of the brainstem. We used immunohistochemistry to analyze 3 autopsy cases with the R521C mutation. As the disease duration becomes longer, there were broader distributions of neuronal and glial FUS/TLS-immunoreactive inclusions.