Fully penetrant genetic mutation results in wide familial variability: a cardiac magnetic resonance focused report

Dilated cardiomyopathy (DCM) is a myocardial disorder characterized by ventricular dilation (LV or biventricular) and systolic dysfunction, with a broad etiological spectrum, comprising numerous genetic and non-genetic causes. Cardiac magnetic resonance (CMR) has become an important tool in guiding the etiological diagnosis in DCM. We present the case of a 37-years old man admitted to our department in order to investigate the diagnosis of DCM using CMR. Cine imaging showed mild left ventricular (LV) dilatation and moderate systolic (LV ejection fraction = 42%) dysfunction, but also apical hypertrabeculation meeting the criteria for non-compaction and late gadolinium enhancement (LGE) images revealed mid-wall fibrosis in the basal and midventricular segments of the inferior interventricular septum (IVS) – typical of non-ischemic DCM. Complete family history revealed the diagnosis of DCM in the mother of the patient and in the maternal grandfather, who had died at 87. After genetic testing of the index patient showed a pathogenic mutation in the TTN (titin) gene (c.79273A>T), cascade genetic testing followed, for his mother, sister, uncle and two cousins who all came back positive for the same mutation. CMR examination of the mother done 6 years prior demonstrated severe LV dilatation and systolic dysfunction (LV ejection fraction = 23%), LV non-compaction and mid-wall IVS fibrosis. CMR examination was performed for the other members of the family and discovered pathological findings in the uncle (normal LV volume and function, but focal mid-wall fibrosis in the inferior IVS) and the male cousin (LV non-compaction), while the female cousin had a normal exam. Using CMR and genetic testing, this case report proves the phenotypic heterogenicity of a completely penetrant titin mutation in the same family. Moreover, CMR is shown to be essential in DCM evaluation, having the ability to guide etiologic diagnosis and to detect alterations such as fibrosis and non-compaction in the absence of LV dilation or dysfunction.