277th ENMC international workshop: Congenital myopathies: revising and revisiting nomenclature and diagnostic guidelines, 21-23 June 2024, Hoofddorp, The Netherlands.

The 277th ENMC workshop on Congenital Myopathies was held in Amsterdam, The Netherlands, on 21-23 June, with 26 clinical, research, and curation experts and patient representatives from five continents. The workshop aimed to 1) establish an updated nomenclature and 2) update recommendations for their diagnostic evaluation. It was agreed that the preferred acronym for congenital myopathies is CMYO. Consensus defined CMYOs as a heterogeneous group of genetic muscle disorders typically presenting perinatally or in infancy with hypotonia and muscle weakness, usually non- or slowly progressive, with distinctive structural, non-dystrophic histopathological features. A nomenclature framework integrating gene, mode of inheritance, and histopathology was proposed, exemplified by "autosomal recessive RYR1-congenital myopathy with cores." Diagnostic consensus emphasized a genetics-first approach, using targeted massively parallel sequencing panels, exome, or genome sequencing, complemented by electromyography, muscle imaging, and biopsy when indicated and available. The workshop highlighted the need for harmonized classification across databases, patient engagement, and global representation to support precise diagnosis, genotype-phenotype correlation, and equitable access to care and research.