Ascorbic acid has been shown to reduce demyelination and improve muscle function in a transgenic mouse model of Charcot-Marie-Tooth disease (CMT1A). Aberrant expression of the myelin protein 22 gene, PMP22 is the cause of CMT1A, and large doses of ascorbic acid are shown to inhibit cAMP-mediated stimulation of human PMP22 expression. A 12-month, randomized, double-blind, placebo-controlled study of ascorbic acid in 117 adult patients compared to 62 receiving placebo found no significant difference between groups in neuropathy scores. Doses of ascorbic acid were 1 g and 3 g daily. The occurrence of adverse events did not differ between groups. 
COMMENT. Similar negative results were obtained in a placebo-controlled trial of ascorbic acid (30 mg/kg/day) in 81 children with CMT1A (2-16 years of age).