[Hereditary spastic paraplegia in Japan]

Abstract

The Japan Spastic Paraplegia Research Consortium (JASPAC) is conducting a nationwide clinical and genetic survey of patients with HSP in Japan. To date (July 20, 2011), 375 index patients with HSP from 42 prefectures in Japan have been registered. In 148 Japanese ADHSP families, SPG4 was the most common form, accounting for 47%, followed by SPG31 (4%), SPG3A (3%), SPG8 (1%), and SPG10 (1%). Meanwhile, preliminary data showed that SPG11 and ARSACS were common in Japanese ARHSP families. Since the genes in approximately 40% of ADHSP and 80% of ARHSP cases remain unknown, we aim to identify the new genes responsible for HSP. We are now searching for a novel gene responsible for ARHSP with optic atrophy and neuropathy. To date, non-Quebec patients with ARSACS have been found in the Mediterranean area, Europe and Japan. Although Quebec patients show a homogeneous phenotype, Japanese patients exhibit some atypical clinical features, as follows: slightly later onset than that in Quebec patients, absence of retinal hypermyelination, intellectual impairment, and lack of spasticity. Recently, we found characteristic MRI findings in eight Japanese ARSACS patients, who all exhibited linear hypointensity in the pons and a hypointense area in the middle cerebellar peduncles in T(2) weighted and FLAIR images.