NPPB and polyneuropathy: We found that (1) diflunisal treatment significantly delayed the progression of polyneuropathy, as assessed by the FAP stage and NCS, compared with treatment‐naive patients and showed similar efficacy to tafamidis treatment; (2) diflunisal and tafamidis treatments both significantly decreased heart radiotracer uptake, as evaluated by the volumetric H/CL ratio on 99mTc‐PYP SPECT, and stabilized IVSd and LVPWd on echocardiography and pro‐BNP levels in the blood.