Renal Involvement in Systemic Amyloidosis Caused by Monoclonal Immunoglobulins

Non-Immunoglobulin Amyloidosis-Mediated Kidney Disease: Emerging Understanding of Underdiagnosed Entities

Amyloidosis is a complex group of rare disorders characterized by the deposition of misfolded proteins in the extracellular space of various tissues and organs, leading to progressive organ dysfunction. The kidneys constitute a very common site affected, most notably by immunoglobulin-mediated (light chain, heavy chain, and light and heavy chain amyloidosis), but other types that include serum amyloid A (AA) amyloidosis and leukocyte chemotactic factor 2 amyloidosis, along with mutant proteins in several hereditary forms of amyloidosis such as transthyretin, fibrinogen α-chain, gelsolin, lysozyme, and apolipoproteins AI/AII/AIV/CII/CIII amyloidosis have been incriminated as well. The clinical presentation is variable and can range from minimal proteinuria for leukocyte chemotactic factor 2 amyloidosis to a full-blown nephrotic syndrome for AA amyloidosis. Clinical correlation, genetic analysis, and adequate tissue typing through a kidney biopsy are essential to make the correct diagnosis, especially when a family history of amyloidosis is absent. Except for AA and transthyretin amyloidosis, the treatment is usually purely supportive. Kidney transplantation is an acceptable form of treatment for end-stage kidney disease in all types of non-Ig-mediated renal amyloidosis.

Pathologic light chain amyloidosis oligomer detection in urinary extracellular vesicles as a diagnostic tool for response and progression of disease

Light Chain (AL) Amyloidosis is a plasma cell dyscrasia producing amyloidogenic light chains (LC) that misfold and form amyloid deposits that cause damage in vital organs, primarily the heart and kidneys. Urinary extracellular vesicles (uEVs) are nanoparticles produced by renal epithelial cells throughout the nephron. We previously showed that uEVs from active renal AL amyloidosis patients contain LC oligomers that are large (>250kDa), resistant to heat and chemical denaturation, but of low abundance. Renal dysfunction in AL amyloidosis results in high urine protein, compounding technical challenges to use uEVs as analytical tools. In this study, we assess the use of uEVs as analytical diagnostic tools for response and disease progression in AL amyloidosis. Our results suggest that uEV protein concentration, urine volume, and particle concentrations are not directly correlated. Multiple strategies for overcoming non-specific antibody binding in uEV samples were validated in our study. We demonstrated that the sensitivity for pre-clinical testing is improved with a urine sample requirement algorithm that we developed. The findings of our study will provide a pathway toward development of critically needed tools for patient management. Sensitive detection of LC oligomers from a non-invasive urine sample rather than an invasive renal biopsy will reduce patient burden and healthcare costs. The ability to detect LC oligomers in patients with renal progression, despite positive hematologic response; will allow clinicians to confidently treat, but not overtreat, patients at risk of ongoing significant renal injury.

Supportive Care and Symptom Management for Patients With Immunoglobulin Light Chain (AL) Amyloidosis

Immunoglobulin light chain (AL) amyloidosis is a disorder of clonal plasma cells characterized by deposition of amyloid fibrils in a variety of tissues, leading to end-organ injury. Renal or cardiac involvement is most common, though any organ outside the central nervous system can develop amyloid deposition, and symptomatic presentations may consequently vary. The variability and subtlety of initial clinical presentations may contribute to delayed diagnoses, and organ involvement is often quite advanced and symptomatic by the time a diagnosis is established. Additionally, while organ function can improve with plasma-cell-directed therapy, such improvement lags behind hematologic response. Consequently, highly effective supportive care, including symptom management, is essential to improve quality of life and to maximize both tolerance of therapy and likelihood of survival. Considering the systemic nature of the disease, close collaboration between clinicians is essential for effective management.