A novel large deletion in the RYR1 gene in a Belgian family with late-onset and recessive core myopathy

•We report a novel and unusual mutation (large deletion) in the RYR1 gene.•The large RYR1 deletion was associated with late-onset and recessive core myopathy.•Co-occurrence of late-onset/recessive RYR1 core myopathy is exceptionally rare.•This also highlights the growing concept of RYR1-associated core myopathy.

We report a novel and particularly unusual type of mutation, namely, large deletion in the RYR1 gene, in a Belgian family with myopathy: Patients were found to be compound heterozygous and presented a clinico-pathological phenotype characterized by late-onset and recessive myopathy with cores. We depict the clinical, electrophysiological, pathological and molecular genetic characteristics of family members.To date, large deletions in the RYR1 gene have been reported in only two cases. Both involved different mutations and, in sharp contrast to our cases, presented with a very early-onset, neonatal, and a very severe or lethal phenotype. Overview of reported clinico-pathologic phenotypes, also highlights the rarity of combined late-onset/recessive co-occurrence in this group of myopathies with cores. Finally, this report underlines the broadening spectrum in this group of myopathologic disorders and highlights the concept of ‘RYR1-associated/related core myopathies’.