Marfan's Syndrome

The Facts

Marfan's syndrome is a genetic disorder that affects the body's connective tissue, the tissue that makes up our tendons, ligaments, joints, and muscles, including the cardiovascular system and eyes. People with this condition are generally very tall and slim with long arms and fingers. It's quite rare - roughly one American in 5,000 has it.

Causes

Marfan's syndrome is caused by a dominant gene. This means a person only needs to have one copy of the defective gene to have the disease. The abnormal gene is known as FBN1, located on chromosome 15 (in some cases, a second gene on chromosome 5 is also involved). Only one-quarter of cases are caused by "new" or spontaneous mutations. The majority of people inherit the gene from one of their parents; people with Marfan's syndrome have a 50% chance of passing it on to each of their children.

The mutated gene affects the ability to produce fibrillin, a building block of connective tissue. This tough, elastic material connects parts of the body and provides structural support for many body tissues. With Marfan's syndrome, the weakened connective tissue takes a toll on cartilage, tendons, ligaments, bones, heart valves, and large blood vessels.