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There are at least 21 types of amyloidosis of which familial amyloidosis is the only one that is inherited. It is found in families of nearly every ethnic background. In addition, there are over 70 transthyretin (TTR) “mutations” that are associated with hereditary amyloidosis. The deposits in this type are made up of the transthyretin or TTR protein, giving this type the code ATTR (Amyloid transthyretin). The transthyretin protein is manufactured in the liver, and it is a mutation of this protein that causes hereditary amyloidosis. There are other proteins with mutations which can cause familial amyloidosis, but these are very rare. They include apolipoprotein A1, gelsolin, fibrinogen, and lysozyme among others.
TTR is the main constituent of amyloid that deposits preferentially in peripheral nerve giving rise to familial amyloid polyneuropathy (FAP), or in the heart leading to familial amyloid cardiomyopathy. This typically causes numbness and tingling in the arms and legs, dizziness upon standing, and diarrhea. However, each family has its own pattern of organ involvement and associated symptoms. The mode of transmission is autosomal dominant, which means that if you have this type of amyloidosis each of your children has a 50% chance of inheriting the disease. If your child does not inherit the gene, he/she cannot pass it on to future generations. Patients typically begin to see symptom onset as adults.
By examining the DNA of a blood sample it is possible to determine if an individual carries the disease or not. If you carry the disease then biopsies obtained from the rectum or the abdominal fat are 2 ways to identify amyloid deposits. Today's most important methods to diagnose the disease are therefore family history, DNA technology and a biopsy specimen for microscopic examination.
For hereditary (ATTR) amyloidosis, the major therapy is liver transplantation. Since the transthyretin protein which causes familial amyloidosis is made in the liver, replacing this organ removes the source of mutant protein production. A new liver will make only normal transthyretin. At present, medical researchers are evaluating whether or not previously formed amyloid TTR deposits will disappear after liver transplantation.
More information is available from Dr. Benson at the Amyloid Research Group, Indiana University School of Medicine. His site contains a good overview of amyloidosis and he specializes in Familial Amyloidosis. Also, you should review: http://www.ibmc.up.pt/group.php?area=4&grupo=9
http://paramiloidose.tripod.com/index.htm
The Amyloidosis Foundation authored a 12 page booklet for patients/family/caregivers. Please feel free to download the booklet Hereditary Amyloidosis. If you have any trouble with the download, please call using (248) 922-9620 or email us at info@amyloidosis.org.
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