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 6years 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>T, p.Arg162Trp) in 2 symptomatic members. The mutation was also identified in 4 asymptomatic members, including 2 elderly members aged over 78years. 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.
Keywords: Amyotrophic lateral sclerosis; Dysarthria; Elderly asymptomatic carriers; Fasciculation; Hereditary spastic paraplegia; SPG10; Whole exome sequencing.
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