What causes Marfan syndrome?
A single abnormal (mutant) gene on Chromosome 15 causes the condition. This abnormal gene controls production of fibrillin, a very fine fibre in connective tissue throughout the body (the "glue and scaffolding of the body"). Most of the time this gene is inherited from a parent who is also affected. However, about 25% of the cases occur when the abnormal gene appears in an egg or sperm (a spontaneous "new" mutation) producing an affected child from two unaffected parents.
Marfan syndrome is inherited as an "autosomal dominant" condition. This means that someone with Marfan syndrome has a 50-50 chance that each offspring will inherit the condition, regardless of sex. On average 1 in 10 affected children are seriously affected.