Marfan syndrome is an autosomal dominant connective tissue disorder. It is caused by a defect in the FBN1 gene on chromosome 15 that codes for the protein fibrillin-1.
Fibrillin is an important component of connective tissue. This means people with Marfan syndrome have features resulting from abnormal connective tissue.
It affects around 1 in 3,000 people.
The life expectancy of patients used to be around 40-50 years. With the advent of regular echocardiography monitoring and beta-blocker/ACE-inhibitor therapy this has improved significantly over recent years.
Aortic dissection and other cardiovascular problems remain the leading cause of death however.
There are two tests for arachnodactyly to remember: First, ask them to cross their thumb across their palm, if the thumb tip goes past the opposite edge of the hand this indicates arachnodactyly. Next ask them to wrap the thumb and fingers of one hand around the other wrist, if the thumb and fingers overlap this also indicates arachnodactyly.