Amyloidosis is a disease that can affect dogs, cats and other mammals – including us! The disease happens when incorrectly folded proteins are deposited in the tissues of various organs. When these mis-folded proteins build up, they disrupt the normal function of that organ. Common deposition sites in the dog and cat are the kidneys, the liver and the spleen.
In cats and dogs, the most common kind of amyloidosis is called AA amyloidosis. Serum amyloid A protein (SAA) is an acute phase protein that is found in high concentrations in the blood during inflammation. This high concentration of SAA provides a source for protein mis-folding, leading to AA amyloidosis, which can develop as a result of chronic inflammation, chronic infection or cancer.
It is important to note that chronic inflammation, infection and cancer don’t always lead to the formation of amyloid proteins, nor are they always the cause of amyloidosis in animals. Sometimes, amyloidosis is idiopathic, meaning that we can’t find an underlying cause. And sometimes, amyloidosis is familial, or passed on genetically through the blood line.
Familial amyloidosis is seen in Shar-Peis, where the target organ for protein deposition is the kidney. In cats, we see renal (or kidney) amyloidosis in the Abyssinian and hepatic (or liver) amyloidosis in Siamese cats.
Clinical signs of amyloidosis are variable, depending on where the amyloid proteins are deposited. The deposition of protein causes disruption of the normal function of the organ, so in the case of renal amyloidosis, clinical signs of amyloidosis would be the same as those of renal failure - mainly increased water intake and urination, weight loss, depression, and decreased appetite.
In cases of hepatic amyloidosis, clinical signs would point to liver failure. Decreased appetite, vomiting, and lethargy can be seen early on in the disease process. In more advanced liver disease, a yellow tint (jaundice) can be seen in the gums and the whites of the eyes, as can a distended, painful abdomen. Spontaneous hemorrhage (or blood loss) from the liver can occasionally be seen and is life threatening.
Definitively diagnosing amyloidosis can be tricky. If pets present very sick from their apparent illness (either hepatic or renal failure), they will likely need to be stabilized before more invasive testing can be performed. Once stable, biopsies will be needed to diagnose amyloidosis.
Unfortunately, there is currently no cure for amyloidosis. Once found, we cannot reverse the damage caused by the deposition of amyloid protein, but we can try to slow the process of organ failure using medications that target the deposition of amyloid proteins. Otherwise, standard therapies for the medical management of kidney or liver failure are indicated.