Familial amyotrophic lateral sclerosis (ALS) is frequently associated with mutations in the SOD1 gene. We identified a rapidly progressive disease in a patient with an inherited ALS. The identified heterozygous T>A exchange in position 1067 in the SOD1 gene results in an amino acid substitution of lysine for asparagine at position 86 (N86K) of the SOD1 protein. The family history suggested that this autosomal dominantly inherited mutation may be associated with rapidly progressive disease.