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Wednesday 30 March 2011

Hereditary Hemorrhagic Telangiectasia

HHT is a genetic disorder that causes abnormalities of blood vessels. Most of the blood vessels in the body of a person with HHT are normal. However, some of the vessels do have an abnormality. There are two types of blood vessels: arteries and veins. An artery does not usually connect directly a vein. Usually there are very small blood vessels called capillaries that connect artery to a vein. A person with HHT has a tendency to form blood vessels that lack the capillaries between an artery and vein. This means that arterial blood under high pressure flows directly into a vein without first having to squeeze through the very small capillaries. This place where an artery is connected directly to a vein tends to be a fragile site that can rupture and result in bleeding. When a blood vessel is abnormal this way, it is called telangiectasia. Telangiectases tend to occur at the surface of the body such as the skin and the mucous membrane that lines the nose. The telangiectases of HHT occur primarily in the nose, skin of the face, hands, and mouth and the lining of the stomach and intestines, lungs, liver and brain. We are still not sure why these abnormalities occur in these specific areas.

The study I picked had to deal with mutations of HHT found in Spanish families. They identified two different mutations, 22 ALK1 mutations and 15 ENG mutations, in independent Spanish families affiliated with HHT. They identified mutations in 37 unrelated families. An analysis of all the symptoms were recorded for each patient that was analyzed. They found there were more abnormalities in HHT1 patients than HHT2 patients. Twenty-two mutations in ALK1 and fifteen in ENG genes were identified. Many of them, almost half, represented new mutations in ALK1 and in ENG.

Overall, ALK1 mutations (HHT2) were predominant over ENG mutations (HHT1) in the Spanish population. This data goes along with another previous study that was based on Mediterranean countries such as France and Italy, but different to Northern Europe or North America. There was a significant increase of abnormal blood vessels associated with HHT1 over HHT2 in these families.

Christina Moreno

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