**Acknowledgements**

This work was partly supported by the Grants-in-Aid for Scientific Research, the Japan Society for the Promotion of Science (no. 24500548 and 17 K17925), and by endowments from MSD and Takeda Pharmaceutical Company.

#### **Conflict of interest**

Keiji Uchida holds a patent on the quantitative tactile examination device. The other authors declare that they have no competing interests.

### **Author details**

Junichi Danjo<sup>1</sup> \*, Sonoko Danjo1 , Hideyuki Sawada2 , Keiji Uchida3 and Yu Nakamura1

