Reducing Body Myopathy and Other FHL1-Related Muscular Disorders

During the past 2 years, considerable progress in the field of four and a half LIM domain protein 1 (FHL1)-related myopathies has led to the identification of a growing number of FHL1 mutations. This genetic progress has uncovered crucial pathophysiological concepts, thus redefining clinical phenotypes. Important new characterizations include 4 distinct human myopathies: reducing body myopathy, X-linked myopathy with postural muscle atrophy, Emery-Dreifuss muscular dystrophy, and scapuloperoneal myopathy. Additionally, FHL1 mutations have been discovered in rigid spine syndrome and in a single family with contractures, rigid spine, and cardiomyopathy. In this review, we focus on the clinical phenotypes, which we correlate with the novel genetic and histological findings encountered within FHL1-related myopathies. This correlation will frequently lead to a considerably expanded clinical spectrum associated with a given FHL1 mutation.