Are giant axons a pathological marker of charcot‐marie‐tooth neuropathy type 2E?

Background: According to electrophysiological and pathological criteria Charcot Marie Tooth (CMT) disease includes primary demyelinating forms (CMT1) and neuropathies with primary axonal loss (CMT2). In CMT1, genetic analysis provided some associations between characteristic lesions and different proteins. In CMT2, four genes were identified recently (CMT2A, B, D, E); the molecular diagnosis is complex and phenotypical hallmarks are lacking. Objectives: To describe the nerve biopsy in three pedigrees with CMT2E caused by mutations of the neurofilament-light chain gene (NF-L): two pedigrees from Campania sharing a Pro22Ser substitution in the head domain of protein and one pedigree from Apulia with a novel Leu268Prol substitution in the central rod domain. In all three pedigrees electrophysiology was consistent with a mixed, demyelinating and axonal neuropathy. Results: The three patients analysed revealed a primary axonopathy characterized by giant axonal swelling filled with densely packed neurofilaments and some atrophic axons. Conclusions: We propose that, in the diagnostic work up of CMT2, giant axons may orientate towards CMT2E. The pathological alterations detected correlate intuitively with an altered function of the neurofilaments which constitute the axonal cytoskeleton and are critical for radial growth and for axonal transport.