Non-invasive Methods for Earlier Diagnosis of Amyloidosis

Introduction

Amyloidosis is a rare disease condition where the proteins in the body become mutated or changed. This results in a mishap of twisted proteins accumulating on the organs or tissues. The heart, kidneys, liver, and lungs are some of the organs that are usually affected. It can either spread throughout the body or be localized to one area of the body. This article discusses some non-invasive methods that help to diagnose the condition early.

What Is Amyloidosis?

A buildup of a type of protein called amyloid results in a rare condition called amyloidosis. The amyloid proteins are usually seen to be accumulated in organs like the heart, brain, kidneys, spleen, and other parts of the body. Studies show that about seventy percent of people suffering from amyloidosis are men. The disease condition can be acquired or inherited, systemic or local.

Amyloid proteins are accumulated in an extracellular or intracellular pattern, altering the normal functioning of the tissues. Studies show that about ninety percent of amyloid deposits are caused due to the aggregation of misfolded proteins.

How Does Amyloidosis Affect the Body?

Proteins are long molecules that can be stretched out as a long chain. They have various functions that can range from providing energy and immunity to balancing fluids, providing structure, and regulating the various processes in the body. Proteins usually leave the bloodstream after completing their assigned tasks. In a protein misfolding disorder, proteins have abnormal shapes and accumulate on various surfaces of the organs. The body can neither use these proteins nor remove them.

These proteins reach the bloodstream and are deposited on healthy organs. These proteins have an increased tendency to form a chunk and accumulate in many places. They may form a build-up in different organs or various parts of the body. The heart, kidneys, liver, GI (gastrointestinal) tract, joints, skin, and blood vessels can be some areas that can be affected by systemic amyloidosis. In some cases, the amyloid deposit may be too much, which can result in organ failure. Localized amyloidosis usually affects the skin, bladder, and airways.

What Are the Symptoms of Amyloidosis?

The amyloidosis symptoms may vary depending on the type of specific protein and where its fibrils accumulate. For instance, cardiac amyloidosis may show symptoms like fainting or shortness of breath, which can be symptoms of a cardiovascular disorder. Renal amyloidosis, which affects the kidneys, may show swollen feet and legs, which are signs of renal failure. The commonly seen signs and symptoms of amyloidosis include:

• The affected person will be extremely exhausted. This could be due to anemia, a condition where the red blood cells may be lower than normal.

• It could be due to the deposition of abnormal proteins in the GI tract.

• It can be a sign indicating carpal tunnel syndrome (numbness in the hand caused by a pinched nerve).

• The accumulation of amyloid serum A can cause pain in the joints.

• Rashes.

• Bruising around the eyes.

• Swollen abdomen, legs, ankles, or feet.

• Increased bleeding following an injury.

• Increased size of the tongue.

How Is Amyloidosis Diagnosed?

Diagnosing the type of amyloidosis is essential for appropriate treatment. In addition, it is necessary to reduce the specific protein accumulation in the body and all pathological processes linked with the specific protein. The prognosis of the therapy is also influenced by the stage at which the condition is diagnosed. Hence, an early amyloidosis diagnosis reduces the complications and increases the prognosis of treatment. According to recent clinical trials, only a morphological analysis of the biopsy samples from the impaired organ can help to verify the diagnosis of amyloidosis. The golden standard in testing for amyloidosis is the staining of tissue specimens to amyloid-specific Congo red dye with apple green birefringence under polarized light microscopy.

What Are the Non-invasive Methods for Earlier Diagnosis of Amyloidosis?

Imaging Modalities: The advent of scanning research methods like radiography, computed tomography, ultrasound, magnetic resonance imaging, and bone scintigraphy plays a major role in the noninvasive diagnosis of amyloidosis. At present, these methods are only used to diagnose late stages of the condition, where there is a significant accumulation of amyloid proteins in the organs. Hence, imaging is used only to confirm the diagnosis and to get clarification on the type of amyloidosis. For instance, AA (secondary amyloidosis) or AL (primary) amyloidosis is diagnosed with 90 percent sensitivity using I-labeled SAP scintigraphy (a method to visualize large amyloid depositions in the body).

Positron emission tomography (PET) and computed tomography (CT) with thioflavin-analog tracers helpdiagnose IgG light chain amyloidosis in organs that were not previously diagnosed. Studies show that PET was able to identify renal involvement and asymptomatic amyloid in some extra-renal organs in some patients. Research shows that diffusion-weighted magnetic resonance imaging (MRI) is more promising in identifying amyloid nephropathy (kidney damage in renal amyloidosis). However, the sensitivity (the chance of getting a positive result with the disease condition) and specificity (the ability to mark an individual who does not have the disease as negative) of the method in diagnosing the condition remain low.

Analysis of Body Fluids: Analysing body fluids like saliva, blood, urine, and scrapes of mucus membrane epithelia collected without damaging the impaired internal organ is another area of noninvasive diagnosis. Factors and disease markers can be detected by this method before severe systemic abnormalities occur. Attempts to detect amyloid aggregates in urine have been initiated since the 1970s. Currently, many methods have been tried to find the precursor protein of amyloidosis in serum and urine samples.

What Are the Promising Trends in Non-invasive Diagnostics of Amyloidosis?

Since there is no specific non-invasive approach for diagnosing most of the types of amyloidosis, more research is needed for newer approaches. One of the emerging approaches includes the use of specific properties of amyloid aggregates and precursor proteins. They include the amyloid resistance to detergents and proteases, the seeding of amyloidogenic protein monomers by preexisting aggregates, and the recruitment of amyloidogenic monomer protein by synthetic amyloid fibrils. Another approach recently studied is the optimization of monoclonal protein amyloidogenicity assessments. It involves the development of a universal standard for the aggregation of Ig light chains. However, this could be complicated due to the presence of proteins other than the ones involved in amyloidosis. This can be solved to an extent by using ultracentrifugation at high speeds, which eliminates other factors not involved in amyloidosis.

Conclusion

Noninvasive methods for an early diagnosis of amyloidosis are essential for a better prognosis and prevention of complications. The type of amyloidosis should be identified early so that appropriate therapy can be given. In addition, finding the condition at its earlier stages provides a better prognosis. The stage at which the condition is identified has a major impact on the effectiveness of the treatment and the life expectancy after amyloidosis diagnosis.