ATTR-amyloidosis - a systemic disease involving the kidneys

Abstract

ATTR amyloidosis (transthyretin amyloidosis) is a progressive, fatal disease characterized by the accumulation of transthyretin amyloid mainly in the peripheral nervous system (somatic and autonomic) and heart, as well as in the kidneys, gastrointestinal tract, eyeballs, and ligaments, which impairs the normal function of organs and systems. The hereditary form of ATTR amyloidosis, or ATTRv amyloidosis, is found all over the world and is characterized by broad genetic and phenotypic heterogeneity, resulting in late diagnosis. The kidneys are a potential target organ in ATTRv amyloidosis. Clinically, nephropathy is manifested by albuminuria, proteinuria, nephrotic syndrome, or decreased renal function. A nephrologist may be involved in the diagnosis of amyloid nephropathy/ATTRv amyloidosis in a patient with symptoms of renal damage in an endemic region or with a family history of ATTRv amyloidosis, or, more difficult, in the diagnosis of a sporadic case of ATTRv amyloidosis when symptoms of nephropathy were detected in a patient in a non-endemic region without a known family history of amyloidosis. The diagnosis of amyloidosis, especially is sporadic cases, requires the nephrologist to know the specific symptoms, the so-called "red flags" of ATTR amyloidosis that allow suspecting amyloidosis, and methods to confirm the diagnosis. Kidney biopsy in the presence of nephropathy is the gold standard in the diagnosis of amyloidosis. Congo-red staining of biopsy specimens with subsequent visualization of the apple-green birefringence of congophilic masses with polarized light is crucial for histological confirmation of the diagnosis. Immunohistochemistry is used for amyloid typing. The less available method for typing is mass spectrometry of affected tissue. Detection of "red flags" of amyloidosis in a patient with nephropathy makes it possible to diagnose ATTR amyloidosis in some cases without a biopsy, by TTR gene sequencing or myocardial scintigraphy with 99mTc-pyrophosphate. After amyloidosis is diagnosed, it is necessary to conduct a detailed examination for assessing the damage to potential target organs, which requires an interdisciplinary approach. Early diagnosis and disease-modifying therapies can slow the progression of neuropathy and cardiomyopathy, and presumably nephropathy.