ObjectiveDevelopment of biomarkers for Charcot‐Marie‐Tooth (CMT) disease is critical for implementing effective clinical trials. The most common form of CMT, type 1A, is caused by a genomic duplication surrounding the PMP22 gene. A recent report (Neurology 2018;90:e518–3524) showed elevation of neurofilament light (NfL) in plasma of CMT1A disease patients, which correlated with disease severity. However, no plasma/serum biomarker has been identified that is specific to Schwann cells, the most directly affected cells in CMT1A.MethodsWe used the Olink immuno PCR platform to profile CMT1A patient (n = 47, 2 cohorts) and normal control plasma (n = 41, two cohorts) on five different Olink panels to screen 398 unique proteins.ResultsThe TMPRSS5 protein (Transmembrane protease serine 5) was elevated 2.07‐fold (P = <0.0001) in two independent cohorts of CMT1A samples relative to controls. TMPRSS5 is most highly expressed in Schwann cells of peripheral nerve. Consistent with early myelination deficits in CMT1A, TMPRSS5 was not significantly correlated with disease score (CMTES‐R, CMTNS‐R), nerve conduction velocities (Ulnar CMAP, Ulnar MNCV), or with age. TMPRSS5 was not significantly elevated in smaller sample sets from patients with CMT2A, CMT2E, CMT1B, or CMT1X. The Olink immuno PCR assays confirmed elevated levels of NfL (average 1.58‐fold, P < 0.0001), which correlated with CMT1A patient disease score.InterpretationThese data identify the first Schwann cell‐specific protein that is elevated in plasma of CMT1A patients, and may provide a disease marker and a potentially treatment‐responsive biomarker with good disease specificity for clinical trials.

Objective: We evaluated the sensitivity of various rehabilitation and lung function scales to detect differences between people with Charcot-Marie-Tooth (CMT) disease and healthy controls. We also studied whether these measurements are sensitive to disclose changes in patients with CMT disease after rehabilitative treatment.Design: Eight patients with different types of CMT participated in the study.Data were gathered at baseline; at the end of the treadmill training, stretching, respiratory, and proprioceptive exercise (TreSPE) treatment period; and after a washout period of 6 mos. The following instruments were used for data collection: Medical Research Council scale for lower limb strength; Tinetti Balance Scale; Physical Performance Battery; ankle angle, oxygen consumption, and lung function tests; peak treadmill velocity and slope; time to walk 6 m; and CMT Neuropathy Score. The participants underwent TreSPE treatment twice every week for 8 wks.Results: All rehabilitative measures were significantly worse in subjects with CMT disease than in healthy controls. Lung function was always normal except for the maximum expiratory pressure and maximum inspiratory pressure. No dropouts or worsening in any of the different outcome measures were observed after TreSPE. The ankle angle and the time to walk 6 m were the only measures that significantly improved after treatment. Conclusions:The rehabilitative outcome measures used in this protocol are useful in detecting clinical impairment in people with CMT disease. Lung function tests were confirmed to be minimally abnormal in patients with CMT disease. The TreSPE treatment, besides being safe and well tolerated, induced some training effects in CMT neuropathy, in the absence of lung function amelioration and effort tolerance. Follow-up showed that CMT patients should be treated at least twice every year because a regression of all outcome measures to the baseline state was found after a 6-mo washout period.