30 Jun 2020
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A Heterozygous Mutation in the Filamin C Gene Causes an Unusual Nemaline Myopathy With Ring Fibers
Authors:
Teresinha Evangelista, MD, Xavière Lornage, PhD, Pierre G Carlier, MD, PhD, Guillaume Bassez, MD, PhD, Guy Brochier, PhD, Anais Chanut, MS, Emmanuelle Lacène, MS, Mai-Thao Bui, BS, Corinne Metay, PharmD, PhD, Ursula Oppermann, PhD, Johann Böhm, PhD, Jocelyn Laporte, PhD, Norma B Romero, MD, PhD
Autosomal dominant pathogenic variants in the filamin C gene (FLNC) have been associated with myofibrillar myopathies, distal myopathies, and isolated cardiomyopathies. Mutations in different functional domains of FLNC can cause various clinical phenotypes. A novel heterozygous missense variant c.608G>A, p.(Cys203Tyr) in the actin binding domain of FLCN was found to cause an upper limb distal myopathy (MIM #614065). The muscle MRI findings are similar to those observed in FLNC-myofibrillar myopathy (MIM #609524). However, the muscle biopsy revealed >20% of muscle fibers with nemaline bodies, in addition to numerous ring fibers and a predominance of type 1 fibers. Overall, this case shows some unique and rare aspects of FLNC-myopathy constituting a new morphologic phenotype of FLNC-related myopathies.