Footnotes

• MS and HT contributed equally.

• Contributors MS and HT contributed equally. MS, HT, HS and AK designed research project, and performed pathological analysis and drafted the manuscript for intellectual content. TM, TF and KM collected clinical data. YH, TI and OO designed the genetic testing.

• Funding This work was supported in part by JSPS Grants-in-Aid for Scientific Research to HS (19K07841), HT (19K16908), TI (17K09750) and AK (19H01061 and 19H05559) and Grants-in-Aid from the Research Committee of CNS Degenerative Disease, Research on Policy Planning and Evaluation for Rare and Intractable Diseases, Health, Labour and Welfare Science Research Grants, the Ministry of Health, Labour and Welfare, Japan to OO and AK.

• Competing interests None declared.

• Provenance and peer review Not commissioned; externally peer reviewed.

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