GDF15 and Charcot-Marie-Tooth disease: A 2.7-fold increase in GDF15 was seen in CMT patient sera compared to controls (P < 0.0001), and similar elevations were observed in the GARS/AARS (2.5-fold, P = 0.005), PMP22d (2.1-fold, P < 0.0001) groups (Fig. 7A), with a threshold of > 411.8 pg/ml distinguishing CMT patients from controls with a sensitivity of 94% and a specificity of 93%.