The goal of this study is to better understand the progression of CMT1A and identify risk factors influencing disease course. CMT1A, the most common hereditary peripheral neuropathy, shows high variability in individual phenotypes despite genetic similarity. Key objectives include analyzing determinants of phenotypic expression and documenting symptom variability over five years to capture disease dynamics. Although incurable, novel CMT therapies are in development. Proving efficacy is challenging due to slow progression and limited sensitive outcome measures. This study aims to validate biomarkers (DNA/epigenetics and RNA/RT-PCR) and sensitive outcome measures from blood and skin of CMT patients over five years to support clinical therapy trials. Approximately 25 healthy volunteers will serve as controls, providing blood and skin samples for biomarker validation. Additionally, the project will build a tissue collection (skin, blood, and cultured fibroblasts) from CMT patients of various subtypes for unrestricted scientific research, especially for the German CMT-NET network (NCT03386266). Scientific partners have free access to samples and data for research (commercial use is excluded). Currently, this collection includes over 100 standardized skin biopsies from CMT1A patients and is Germany's only repository for hereditary neuropathy tissue samples.