Amyloidosis: What it Is & How it Affects the Kidneys

Amyloidosis, a little understood disease could wreck your kidneys

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SO, WHAT IS AMYLOIDOSIS?

The term "amyloid" refers to an abnormal protein, one with a characteristic and specific appearance. This appearance is something that can only be appreciated under a thorough microscopic exam and abnormal pathological deposition of amyloid is called amyloidosis. The culprit protein in question can have different chemical characteristics, but often has a specific and similar tell-tale appearance when looked at under a microscope.

Abnormal deposition and build-up can hurt the organ where it happens. The kidney is a commonly involved organ, although other organs like the heart, liver, and the nerves are also considered fair game. Hence, how clinical amyloidosis presents depends on the organ affected and the severity of deposition. 

This article will cover the features of amyloidosis that involve the kidney. 

WHAT CONDITIONS LEAD TO AMYLOIDOSIS OF THE KIDNEY?

As mentioned above, the term amyloidosis refers to the abnormal deposition of a an abnormal protein (of a specific appearance) that hurts the kidneys' function. Disease conditions that can lead to this include:

  • Primary Amyloidosis is a condition often seen in association with production of abnormally high production of antibodies by a particular type of immune cell called the "plasma cell". A common condition where this can occur is Myeloma, a type of a blood cancer, although primary amyloidosis can occur in absence of a myeloma. The antibodies can deposit in the kidneys filter (called the glomerulus) and overwhelm its ability to filter them out in to the urine. Think of it as a phenomenon akin to dumping gunk in to your kitchen sink that does not belong there. What happens to the plumbing of the kitchen sink? It eventually shuts down/clogs, right? A similar process (although not as simplistic) happens in the glomerulus and can eventually lead to the kidneys shutting down completely. The kidney is not the only organ affected though. Depending on where the deposition occurs, the disease states could range from food malabsorption from the gut, to congestive heart failure, to even carpal tunnel syndrome.
  • Secondary Amyloidosis. As the name suggests, this abnormal protein amyloid can deposit secondary to its overproduction in multiple disease states. These conditions include entities associated with chronic inflammation like rheumatoid arthritis, COPD, tuberculosis, systemic lupus erythematosus, etc. Other symptoms can be similar to primary amyloidosis. The abnormal protein looks similar to that seen in primary amyloidosis, and just looking at a biopsy may or may not help in differentiating between primary and secondary amyloidosis.
  • Dialysis-related Amyloidosis is a specific entity that is seen in dialysis patients. A specific protein called the beta-2 microglobulin can build in the blood to extremely high levels since it is not removed by dialysis. Once it deposits, its effects can be similar to primary or secondary amyloidosis, and vary with where the deposition occurred. 

WHAT SYMPTOMS COULD YOU HAVE IF YOU HAVE AMYLOIDOSIS OF THE KIDNEY? 

This article will not go into the details of symptoms that can occur from deposition of amyloid in organs other than the kidneys. For that, the reader is referred to other excellent sources on the internet.

Symptoms/signs of abnormal amyloid deposition, as far as the kidneys go, could include: 

  • Abnormally high protein loss in the urine. This is called proteinuria, and occurs due to damage to the kidneys' filter, the glomerulus. In worst cases, this can present as the "nephrotic syndrome
  • Kidney failure
  • Edema, or swelling in the legs, or even around the eyes 
  • High cholesterol levels (mechanism beyond the scope of this article)
  • Low albumin levels in the blood
  • Pain in the joints. If the deposition occurs in the wrists, it could cause carpal tunnel syndrome 

HOW IS AMYLOIDOSIS TREATED

While complications from failure of the individual organs need to be treated, specific treatment is aimed at reducing the production of this abnormal protein, or the amyloid. This could range from chemotherapy using a drug called melphalan, to stem cell transplant which also has been shown to help. 

You will need input from your nephrologist and oncologist to proceed further! 

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