Mitochondrial dysfunction in human PMD fibroblasts is prevented by NAC. Intracellular peroxide levels (DCF probe) (A); Intracellular (DHE probe) and mitochondrial (MitoSOX probe) superoxide levels (B); Inner mitochondrial membrane potential (C); mitochondrial respiration (D), and ATP content (E) were quantified in human control and PMD fibroblasts with or without NAC treatment (n = 4/genotype). In C, the numeric value above the line corresponds to the percentage of depolarized cells in Pelizaeus‐Merzbacher disease fibroblasts after treatment with NAC (100 μM) during 24 h. DCF = dichlorofluorescein, DHE = dihydroethidium, TMRE = tetramethylrhodamine ethyl ester, CTL = control, PMD = Pelizaeus‐Merzbacher disease. Values are expressed as the mean ± SD. Statistical analysis was performed by one‐way ANOVA and Tukey's HSD post hoc (A, C and E) and Student's t‐test (B and D); *P < 0.05, **P < 0.01; ***P < 0.001.