The aims of this study were to (1) determine the prevalence and clinical associations of anti-FHL1 autoantibodies, in a large cohort of patients with IIM; (2) to evaluate when anti-FHL1 autoantibodies are present in the course of the disease, and if autoantibody levels vary over time; and (3) to identify its presence in other autoimmune and neuromuscular diseases (NMDs). Here, FHL1 is linked to neuromuscular disease.