PMP22 and Charcot-Marie-Tooth disease: Since the affected family members had a more severe demyelinating CMT phenotype compared to CMT1A we performed transcript quantitation analysis to quantify the PMP22 transcript levels in skin biopsy samples containing Schwann cells from epidermal myelinated nerve fibres, using a custom Nanostring platform that was developed to detect elevated levels of PMP22 in CMT1A.20 After standardizing transcript counts relative to Schwann cell-specific normalizing genes, the PMP22 transcript levels in duplicate skin biopsies were markedly increased compared to known controls and disease controls (CMT1A).