• genotype–phenotype correlations;
  • RBM;
  • reducing bodies;
  • muscle inclusions;
  • four-and-a-half LIM domain 1 protein


Introduction: Reducing body myopathy is a rare X-linked myopathy. It is characterized by intracytoplasmic inclusions that stain with menadione–nitroblue tetrazolium. It is caused by mutations in the FHL1 gene, which encodes the four-and-a-half LIM domain 1 protein (FHL1). Methods: We performed a clinical, muscle MRI, and histopathological characterization and immunoblot and genetic analysis of the FHL1 protein in a family with 4 individuals affected by reducing body myopathy. Results: We identified a novel missense mutation in FHL1 (c.449G>C; p.C150S). The patients presented with asymmetric proximal weakness and scoliosis. Both of the boys had a more severe course with earlier onset, contractures, and death due to heart failure at 14 and 18 years of age, respectively. MRI revealed fatty infiltration of posteromedial thigh and paraspinal muscles. Histopathological findings showed FHL1-immunoreactive inclusions. Immunoblot analysis revealed a 50% reduction of FHL1 protein. Conclusion: In this study we highlighted diagnostic clues in this myopathy and compared our data with the literature. Muscle Nerve, 2013