Marfan's syndrome pathophysiology
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Overview
Pathophysiology
Marfan syndrome has been linked to a defect in the FBN1 gene on chromosome 15,[1] which encodes a glycoprotein called fibrillin-1. Fibrillin is essential for the formation of the elastic fibers found in connective tissue, as it provides the scaffolding for tropoelastin.[2] Elastic fibers are found throughout the body but are particularly abundant in the aorta, ligaments and the ciliary zonules of the eye, consequently these areas are among the worst affected. Without the structural support provided by fibrillin many connective tissues are weakened, which can have severe consequences for support and stability.
Marfan syndrome is inherited as a dominant trait. In so far as the pattern of inheritance is dominant, people who have inherit just one affected FBN1 gene from either parent will develop Marfan syndrome. This expression of the syndrome can range from mild to severe.
A related disease has been found in mice, and the study of mouse fibrillin synthesis and secretion, and connective tissue formation, has begun to further our understanding of Marfan syndrome in humans. It has been found that simply reducing the level of normal fibrillin-1 is associated with a Marfan-related disease in mice.[3]
High levels of Transforming growth factor beta (TGFβ) are associated with inflammation and also play an important role in Marfan syndrome. Ordinarily, Fibrillin-1 binds TGFβ and inactivates it. In Marfan syndrome, reduced levels of fibrillin-1 allow activated TGFβ to damage the lungs and heart. Researchers now believe that the inflammatory effects of TGF-β, on the lungs, heart valves, and aorta weaken the connective tissues and cause the features of Marfan syndrome. In so far as angiotensin II receptor blockers (ARBs) reduce TGF-β, these agents have been administered to young Marfan syndrome patients, and the expansion of the aorta was indeed reduced.[4]
Genetics
A defect in the gene TGFβR2 on chromosome 3, a receptor protein of TGFβ, has also been related to Marfan syndrome.[5] Marfan syndrome can often be confused with Loeys-Dietz syndrome, a similar connective tissue disorder resulting from mutations in the TGFβ receptor genes TGFβR1 and TGFβR2.[6]
References
- ↑ McKusick V (1991). "The defect in Marfan syndrome". Nature. 352 (6333): 279–81. PMID 1852198.
- ↑ Cotran. Robbins Pathologic Basis of Disease. Philadelphia: W.B Saunders Company. 0-7216-7335-X. Unknown parameter
|coauthors=ignored (help) - ↑ Lygia Pereira; et al. (1999). "Pathogenetic sequence for aneurysm revealed in mice underexpressing fibrillin-1". Proceedings of the National Academy of Sciences. 96 (7): 3819-3823.
- ↑ Pyeritz RE (2008). "A small molecule for a large disease". N. Engl. J. Med. 358 (26): 2829–31. doi:10.1056/NEJMe0804008. PMID 18579819. Unknown parameter
|month=ignored (help) - ↑ Entrez Gene (2007). "TGFBR2 transforming growth factor, beta receptor II" (Entrez gene entry). NCBI.
- ↑ "Related Disorders: Loeys-Dietz". National Marfan Foundation.