A 16-year-old girl presented with progressive bilateral lower limb weakness for 3 years. Examination revealed tongue fasciculations, muscle wasting, and extensor plantar responses. Nerve conduction studies revealed motor-sensory axonal polyneuropathy. MRI brain showed multifocal cavitating white matter disease with diffusion restriction (figures 1 and 2). Exome sequencing revealed heterozygous missense variation c.775C>T(p.Arg259Cys) in exon 8 of the MFN2 gene, pathogenic for Charcot-Marie-Tooth disease 2A (CMT2A).