IGFBP5 protein levels were more than 5-fold up-regulated in 6 patients with DNP (P < 0.01, one-way ANOVA) (see electronic supplementary Table 2 for clinical characteristics of these patients) and in 3 patients with combined diabetic neuropathy and chronic inflammatory demyelinating polyradiculoneuropathy (DNP+CIDP; P < 0.001, one-way ANOVA) as compared to CIDP individuals (Fig. 1b, c) and 50-fold in comparison to healthy controls (P < 0.001, one-way ANOVA). Here, PMP22 is linked to diabetic neuropathy.