[Overlap of neuropathy and myopathy genes: convergence of two entities]

Neuropathies and myopathies have long been studied separately, with little or no overlap described between the two entities. However, the advent of high-throughput molecular biology over the past 20 years led to the discovery of mutations in the same gene causing hereditary myopathies and neuropathies. While this overlap is well known for mitochondrial genes, it is more unexpected for genes such as BAG3, DES, and CRYAB, which are mutated both in myofibrillar myopathies and in neuropathies that may be isolated or associated with muscle phenotypes. More recently, genes involved in multisystemic proteinopathies, such as VCP, MATR3, SQTMS1 and TIA1, have also been associated with various combinations of nerve, brain, muscle, and bone diseases. On the other hand, genes such as HSPB8 or SPTAN1, known to be responsible for distal motor neuropathy, have been implicated in distal and/or axial myopathy or in a mixed pattern combining neurogenic and a myogenic component, both electromyographically and histologically. As sequencing techniques improve, unexpected genotype-phenotype correlations are emerging, involving a myopathy gene in peripheral neuropathy and vice versa, leading to a reassessment of the overlap between these two entities.