Frontometaphyseal dysplasia is an X-linked trait primarily characterized by a skeletal dysplasia comprising hyperostosis of the skull and modeling anomalies of the tubular bones. Extraskeletal features include tracheobronchial, cardiac, and urological malformations. A proportion of individuals have missense mutations or small deletions in the X-linked gene, FLNA. We report here our experience with comprehensive screening of the FLNA gene in a group of 23 unrelated probands (11 familial instances, 12 simplex cases; total affected individuals 32) with FMD. We found missense mutations leading to substitutions in the actin-binding domain and within filamin repeats 9, 10, 14, 16, 22, and 23 of filamin A in 13/23 (57%) of individuals in this cohort. Some mutations present with a male phenotype that is characterized by a severe skeletal dysplasia, cardiac, and genitourinary malformations that leads to perinatal death. Although no phenotypic feature consistently discriminates between females with FMD who are heterozygous for FLNA mutations and those in whom no FLNA mutation can be identified, there is a difference in the degree of skewing of X-inactivation between these two groups. This observation suggests that locus heterogeneity may exist for this disorder.
Mild skeletal muscle symptoms might be accompanied with severe cardiac disease, sometimes indicating a serious inherited disorder. Very often it is a cardiologist who refers a patient with cardiomyopathy and/or cardiac arrhythmia and discrete muscle disease for neurological consultation, which helps to establish a proper diagnosis. Here we present three families in which a diagnosis of skeletal muscle laminopathy was made after careful examination of the members, who presented with cardiac arrhythmia and/or heart failure and a mild skeletal muscle disease, which together with positive family history allowed to direct the molecular diagnostics and then provide appropriate treatment and counseling.
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