PMP22 and Charcot-Marie-Tooth disease type 1A: For this reason, it appeared to not be a reliable tool in most studies to discriminate patients with CMT1A from healthy subjects, or as a surrogate endpoint A novel skin biopsy to precisely assess the PMP22 expression level (by RT-PCR and immunoelectron microscopy) as a candidate biomarker for CMT1A clinical trials has recently been developed [43,44].