Treatment of all types of amyloidosis is currently based on the following principles:
- Reducing the supply of amyloid forming precursor proteins.
- Supporting the function of organs containing amyloid.
When amyloid precursor protein supply is controlled:
- existing amyloid deposits often regress (become smaller)
- new amyloid deposits stop appearing
- organ function is often preserved and may also recover
Reducing variant TTR supply: liver transplantation
Liver transplantation may be helpful for some patients with hereditary ATTR amyloidosis, mainly for patients with the Val30Met mutation. Liver transplantation is not a treatment for wild type ATTR amyloidosis.
All the TTR in the blood, which forms the amyloid deposits everywhere except in the eye and the blood vessels around the brain, is made in the liver. Liver transplantation is therefore a treatment option for some patients with hereditary ATTR amyloidosis. The liver which forms the abnormal, ‘variant’ TTR is removed and replaced by a donor liver making normal, ‘wild type’ TTR. The aim is to prevent the formation of further amyloid deposits by reducing the supply of the amyloidogenic precursor TTR.
Liver transplantation has been performed in hundreds of patients with hereditary ATTR amyloidosis around the world. In many cases this has been successful, leading to stabilisation of disease. Success is greatest when transplantation is performed:
- early in the course of disease before there has been too much damage to the nerves or the heart
- in younger patients in patients with the TTR Val30Met mutation
Unfortunately, in some patients amyloid deposits in the heart have continued to progress even after transplantation. It seems that the abnormal TTR fibrils which formed amyloid deposits before the liver transplantation act as a template encouraging deposition of normal TTR as amyloid. Thus the normal TTR protein (wild type TTR) produced by the new liver builds up on top of the existing amyloid deposits containing the abnormal TTR. This problem has appeared most often in older patients with mutations other than Val30Met.
For hereditary ATTR amyloidosis, combined heart and liver transplant has been performed in a few dozen cases around the world. This operation is only an option for a minority of patients, and it carries significant risks.
Most patients with wild type ATTR amyloidosis are too elderly to undergo a heart transplant. The risk of complications from this major operation is high with advanced age. But heart transplantation may be an option for younger, otherwise healthy patients with this condition. The 2 patients who presented to the NAC before age 60 with senile systemic amyloidosis survived 10 and 20 years after heart transplantation.
Supporting amyloidotic organ function
In all types of amyloidosis it is important that treatment should support the function of organs containing amyloid. In ATTR amyloidosis this may include: