SELENON and congenital myopathy with cores: Rigid spine muscular dystrophy-1 (OMIM 602771), desmin-related myopathy with Mallory bodies, congenital myopathy with fiber-type disproportion (OMIM 255310), and severe classic multiminicore myopathy have the same severe disease spectrum and are caused by a pathogenic biallelic or compound heterozygous mutation in the SEPN1 gene (OMIM 606210) located on chromosome 1p36.