However, when taking into account the CMT1A disease severity based on CMTES, we found that plasma GDF15 correlated with disease severity (simple linear regression, R2 = 0.4727, P = 0.0280, Fig. 3D) whereas we could not demonstrate the same for NFL (Fig. 3E). The gene discussed is GDF15; the disease is Charcot-Marie-Tooth disease type 1A.