Why is Marfan syndrome autosomal dominant?

Marfan syndrome is classified as autosomal dominant because it results from mutations in the FBN1 gene, which encodes the connective protein fibrillin-1. This mutation affects only one copy of the gene, meaning that an individual only needs to inherit the mutated gene from one parent to express the condition. The dominant inheritance pattern allows the syndrome to manifest even if the other copy of the gene is normal, leading to various symptoms affecting connective tissues, including those in the heart, eyes, and skeleton. Consequently, affected individuals have a 50% chance of passing the mutated gene to their offspring.