A Clinical Diagnosis of Laminopathy without Systolic Dysfunction: When Does Nuclei Malformation Start?

Nuclear shape abnormalities in laminopathy are well known to occur in patients with cardiac systolic dysfunction. However, those in patients without systolic dysfunction are still unclear. We herein report a 42-year-old man who presented with advanced atrioventricular block without systolic dysfunction. Genetic testing identified a laminopathic mutation, c.497G>C, and an endocardial biopsy was performed. The hyperperfine structure on electron microscopy showed malformation of the nuclei, euchromatic nucleoplasm, and partial existence of heterochromatin clumps. Intrusion of heterochromatin into the nuclear fibrous lamina was observed. Cardiomyocyte nuclear shape abnormalities were observed before the progression of systolic dysfunction.