How is Marfan syndrome inherited?
Everyone has two copies of the fibrillin gene – one comes from mum and the other from dad. Only one copy of the fibrillin gene needs to contain a mistake to cause Marfan syndrome. Such genetic faults are said to be ‘dominant’. 75% of people with Marfan syndrome have inherited the faulty fibrillin gene from an affected parent. In 25% of cases, however, the gene fault occurs for the first time in the affected person. Although that person has no family history of Marfan syndrome, he/she could pass the faulty fibrillin gene on to his/her children. Every time someone with Marfan syndrome has a child there is a 1 in 2 – or 50:50 – chance that the child will inherit the faulty copy of the fibrillin gene. This is called ‘dominant inheritance’ (see diagram). A child who inherits a faulty copy of the fibrillin gene is likely to develop Marfan syndrome, although he/she may develop different problems to his/her parent.
