Pathogenic mutations in the KIF5A-SPG10 gene, encoding the kinesin HC5A, can be associated with autosomal dominant hereditary spastic paraplegia (ADHSP). It accounts for about 10% of the complicated forms of ADHSP. Peripheral neuropathy, distal upper limb amyotrophy, and cognitive decline are the most common additional clinical features. We examined a 66-year-old Japanese woman manifesting gait disturbance and spastic dysarthria for 6 years with positive family history. She showed evidence of upper and lower motor neuron involvement and fasciculations, thus mimicking amyotrophic lateral sclerosis (ALS). Genetic analysis revealed a heterozygous variant in KIF5A (c.484C &gt
T, p.Arg162Trp) in 2 symptomatic members. The mutation was also identified in 4 asymptomatic members, including 2 elderly members aged over 78 years. Electromyography in the 2 symptomatic members revealed evidence of lower motor neuron involvement and fasciculation potentials in distal muscles. This report describes the first known Asian family with a KIF5A mutation and broadens the clinical and electrophysiological spectrum associated with KIF5A-SPG10 mutations. Given that our cases showed pseudobulbar palsy, fasciculation and altered penetrance, KIF5A-SPG10 might well be considered as a differential diagnosis of sporadic ALS.