FHL1 and rigid spine syndrome: Mutations in the FHL1 gene, encoding FHL-1, have been linked to the development of five distinct skeletal muscle diseases, including reducing body myopathy (RBM), X-linked myopathy with postural muscle atrophy (XMPMA), scapuloperoneal myopathy (SPM), rigid spine syndrome (RSS), and Emery-Dreifuss muscular dystrophy (EDMD) [176].