It is sometimes inherited as a dominant trait. It is carried by a gene called FBN1, which encodes a connective protein called fibrillin-1. People have a pair of FBN1 genes. Because it is dominant, people who have inherited one affected FBN1 gene from either parent will have Marfan's. Parents have a 50/50 chance of passing on the gene to their children.
People with Marfan's are typically tall, with long limbs and long thin fingers.
In addition to being a connective protein that forms the structural support for tissues outside the cell, fibrillin-1 binds to another protein, Transforming growth factor beta (TGF-β). TGF-β can cause inflammation. Researchers now believe that the inflammatory effects of TGF-β, at the lungs, heart valves, and aorta, weaken the tissues and cause the features of Marfan syndrome. Since angiotensin II receptor blockers (ARBs) also reduce TGF-β, they have tested this by giving ARBs (losartan, etc.) to young Marfan syndrome patients, and the growth of the aorta was indeed reduced.
It is named after Antoine Marfan, the French pediatrician who first described the condition in 1896 after noticing striking features in a 5 year old girl. The gene linked to the disease was first identified by Francesco Ramirez at the Mount Sinai Medical Center in New York City in 1991.
A transgenic mouse has been created carrying a single copy of a mutant fibrillin 1, a mutation similar to that found in the human fibrillin 1 gene that is known to cause Marfan syndrome. This mouse strain recapitulates many of the features of the human disease and promises to provide insights into the pathogenesis of the disease. It has been found that simply reducing the level of normal fibrillin-1 causes a Marfan-related disease in mice.
Transforming growth factor beta (TGFβ) plays an important role in Marfan syndrome. Fibrillin-1 indirectly binds a latent form of TGFβ keeping it sequestered and unable to exert its biological activity. The simplest model of Marfan syndrome suggests that reduced levels of fibrillin-1 allow TGFb levels to rise due to inadequate sequestration. Although it is not proven how elevated TGFb levels would be responsible for the specific pathology seen with the disease, an inflammatory reaction releasing proteases that slowly degrade the elastin fibers and other components of the extracellular matrix is known to occur. The importance of the TGFb pathway was confirmed with the discovery of a similar syndrome Loeys-Dietz syndrome involving the TGFβR2 gene on chromosome 3, a receptor protein of TGFβ. Marfan syndrome has often been confused with Loeys-Dietz syndrome, because of the considerable clinical overlap between the two syndromes.
Because of the underlying connective tissue abnormalities that cause Marfan syndrome, there is an increased incidence of dehiscence of prosthetic mitral valve. Care should be taken to attempt repair of damaged heart valves rather than replacement.
During pregnancy, even in the absence of preconceived cardiovascular abnormality, women with Marfan syndrome are at significant risk of acute aortic dissection, which can be lethal if untreated. For this reason, women with Marfan syndrome should receive a thorough assessment prior to conception, and echocardiography should be performed every 6-10 weeks during pregnancy, to assess the aortic root diameter. Most women however tolerate pregnancy well and safe vaginal delivery is possible.
Regular checkups by a cardiologist are needed to monitor the health of the heart valves and the aorta. The goal of treatment is to slow the progression of aortic dilation and damage to heart valves by eliminating arrythmias, minimizing the heart rate, and minimizing blood pressure. Beta blockers have been used to control arrythmias and slow the heart rate. Other medications might be needed to further minimize blood pressure without slowing the heart rate, such as ACE inhibitors and angiotensin II receptor antagonists, also known as angiontensin receptor blockers (ARBs). If the dilation of the aorta progresses to a significant diameter aneurysm, causes a dissection or a rupture, or leads to failure of the aortic or other valve, then surgery (possibly a composite aortic valve graft [CAVG] or valve-sparing procedure) becomes necessary. Although aortic graft surgery (or any vascular surgery) is a serious undertaking it is generally successful if undertaken on an elective basis. Surgery in the setting of acute aortic dissection or rupture is considerably more problematic. Elective aortic valve/graft surgery is usually considered when aortic root diameter reaches 50 millimeters (2.0 inches), but each case needs to be specifically evaluated by a qualified cardiologist. New valve-sparing surgical techniques are becoming more common. As Marfan patients live longer, other vascular repairs are becoming more common, e.g. repairs of descending thoractic aortic aneurysms and aneurysms of vessels other than the aorta.
The skeletal and ocular manifestations of Marfan syndrome can also be serious, although not life-threatening. These symptoms are usually treated in the typical manner for the appropriate condition. This can also affect height, arm length, and life span. The Nuss procedure is now being offered to people with Marfan syndrome to correct 'sunken chest' or (pectus excavatum). Because Marfan may cause spinal abnormalities that are asymptomatic, any spinal surgery contemplated on a Marfan patient should only follow detailed imaging and careful surgical planning, regardless of the indication for surgery.
Clinical trials have been conducted of the drug acetazolamide in the treatment of symptoms of dural ectasia. The treatment has demonstrated significant functional improvements in some sufferers. Other medical treatments, as well as physical therapy, are also available.
Treatment of a spontaneous pneumothorax is dependent on the volume of air in the pleural space and the natural progression of the individual's condition. A small pneumothorax might resolve without active treatment in 1 to 2 weeks. Recurrent pneumothoraces might require chest surgery. Moderately sized pneumothoraces might need chest drain management for several days in a hospital. Large pneumothoraces are likely to be medical emergencies requiring emergency decompression.
Research in laboratory mice has suggested that the angiotensin II receptor antagonist losartan, which appears to block TGF-beta activity, can slow or halt the formation of aortic aneurysms in Marfan syndrome. A large clinical trial sponsored by the National Institutes of Health comparing the effects of losartan and atenolol on the aortas of Marfan patients is scheduled to begin in early 2007, coordinated by Johns Hopkins.
Genetic counseling and specialized clinics are available at many academic medical centers for affected persons and family members.
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