Filamin C Truncating Variant Causes Severe Conduction Defects and Mild Cardiomyopathy

Filamin C (FLNC), recently identified as a causative gene of cardiomyopathy, is widely expressed in cardiomyocytes and is involved in signal transduction between the sarcomere and the plasma membrane. In general, the FLNC truncating variant causes severe dilated cardiomyopathy. A 70-year-old female was referred to our hospital with advanced conduction defects and underwent pacemaker implantation. Cardiac MRI revealed mild hypertrophic cardiomyopathy. As her father also underwent pacemaker implantation due to a cardiac conduction defect, the presence of familial cardiac arrhythmia was suspected. A whole-exome sequencing identified the FLNC truncating variant (NM_001458.5 FLNC:c.592_593del, p.Cys198Argfs*40). We experienced an FLNC-related cardiomyopathy case with predominantly advanced conduction defects, which postulated that the variant mainly affected the conduction system.