Marfan Syndrome FBN1 Autosomal Dominant

A 28-year-old man presents to the cardiology clinic with a family history of sudden cardiac death. His father died at age 35 from aortic dissection, and his paternal grandfather had a similar presentation. On examination, the patient is tall with arachnodactyly, pectus carinatum, and a systolic murmur. Echocardiography reveals aortic root dilatation at the sinuses of Valsalva with a Z-score of 2.8. Genetic testing confirms a heterozygous pathogenic mutation in the FBN1 gene on chromosome 15q21.1. The pedigree pattern shown in the diagram, marked as **A**, demonstrates affected individuals in every generation with male-to-male transmission. Which of the following best describes the inheritance pattern and its implications for this patient's siblings?