Marfan syndrome (MFS) is a multisystem disorder of connective tissue that is inherited in an autosomal dominant fashion, and results from mutations in the FBN1 gene on chromosome 15. Diagnosis is challenging as it requires definition of diverse clinical features and input from a variety of specialists. Genetic testing of FBN1 is time consuming, expensive and complex, and may not solve the diagnostic dilemma. Failure to make a diagnosis or making an inappropriate diagnosis of MFS has social, lifestyle and medical consequences for the individual as well as the family.