FAP and Your Kidneys

People with familial amyloid polyneuropathy (FAP) may well have problems with their kidneys. Without treatment, these can lead to serious complications.

How does FAP cause problems with kidneys?

FAP is a rare genetic disease caused by a mutation in the TTR gene. This gene contains the information necessary for cells to produce the transthyretin protein. This protein plays a role in the transportation of retinol (vitamin A) and thyroxine in the body.

Mutations in the TTR gene cause transthyretin proteins to misfold, making them unable to work as they should. The misfolded proteins tend to stick together in clumps or amyloid fibrils. The body cannot easily break down these fibrils, and they build in different tissues. In the kidneys, amyloid buildup causes damage to nephrons (filtering units of the kidney) that can ultimately lead to end-stage renal disease (ESRD) or kidney failure.

What kidney issues are common in FAP?

FAP can affect kidney function in several ways. As the amyloid fibrils build in the kidneys, they can start to cause proteinuria (specifically, microalbuminuria).

A study found that this microalbuminuria usually precedes nephropathy (kidney disease caused by damage to nephrons) by about two years. Patients in this study began showing evidence of kidney failure about five years after microalbuminuria was first evident .

Another study has shown that kidney damage can lead to anemia in FAP patients, due to low levels of erythropoietin, the hormone that generates and maintains red blood cells.

How do doctors treat kidney problems in FAP?

There is currently no cure for FAP. Treatment options focus on treating disease symptoms rather than the underlying cause.

Doctors will regularly monitor the urine of FAP patients for higher-than-normal levels of creatinine and albumin, which indicate proteinuria.

In early disease stages and if kidney function is still good, patients might be considered for a liver transplant. If the disease is still early but the kidneys don’t function properly, then the patient may be a candidate for a simultaneous liver and kidney transplant. The liver produces roughly 95% of the transthyretin protein in the body. So, a liver transplant can help to slow disease progression. However, it will not get rid of amyloids that are already present in the body.

Even after transplants, it is possible for the disease to progress to a point where kidney function is insufficient. If this occurs, or a patient was not a good candidate for the transplants in the first place, hemodialysis can help filter the blood of toxins.

While there is no cure for FAP, research continues into potential treatments aiming to stop or slow its progression.

Last updated: Oct. 8, 2020

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FAP News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health providers with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.