Amyloidosis-related renal injury, diagnostic challenges, and typing in Ukrainian population

Background: Renal amyloidosis is a systemic disorder characterized by extracellular misfolded proteins (amyloid) deposition. In the kidney, amyloid accumulation alters glomerular permeability, damages vascular integrity, and ultimately leads to nephrotic syndrome and chronic kidney disease (CKD). Accurate and early amyloid typing is essential for determining prognosis and selecting appropriate therapy; however, different amyloid types often share similar histopathologic features, complicating diagnosis. We described here specific amyloid types associated with distinct clinical presentations and diagnostic patterns of renal amyloidosis unique to the specific patient population. Methods: This retrospective study (over a 10-year period) reviewed adult nephrology patients who underwent kidney at a single Ukrainian center. Amyloidosis cases were classified as AA, AL, or non-typed due to the limitation of mass spectrometry approach methods. Tissue (kidney) was processed using standard renal pathology protocols. Diagnosis and typing integrated light microscopy, Congo red with polarization, immunofluorescence (κ/λ light chains, AA protein), and transmission electron microscopy. Results: Among 13,477 evaluated patients, 1,217 (9.1%) underwent kidney biopsy for suspected systemic amyloidosis. Biopsy-confirmed amyloidosis was identified in 6.9% of kidney biopsies. Patients had a mean age of 63.7 years, and 54.5% were male, which confirms no sex difference in renal amyloidosis prevalence. AL amyloidosis was the most common subtype (62%), followed by AA (16%). Amyloid type remained unclassified in 22% of patients, reflecting limited access to advanced diagnostic tools such as laser-capture microdissection with mass-spectrometry–based proteomics and targeted genetic testing. Distribution across renal compartments showed variability in the frequency of tubular basement membrane involvement; however, no significant class or grade differences were observed. Quantitative assessment revealed no significant differences in glomerular Congo Red–positive area, cortical interstitial fibrosis, or PAMS-positive amyloid deposition among subtypes. Immunoglobulin and complement “contamination” of amyloid deposits was common across all amyloidosis types (with trace signals scored as 0.5), although AA amyloidosis demonstrated slightly more intense IgA, IgG, and IgM deposition. AL-λ was predominant, occurring in 86–88% of AL renal biopsies. Overall, the prevalence of renal amyloidosis in this cohort appeared higher than global estimates, likely influenced by age distribution, referral patterns, and restricted biopsy availability within the Ukrainian healthcare system. Conclusions: In this large, single-center cohort renal amyloidosis was identified at a higher-than-expected frequency, with AL amyloidosis being predominant subtype and high prevalence of AA type in the population; a substantial proportion of cases being untyped due to diagnostic limitations. Renal amyloid deposition and the resulting nephrotic syndrome represent a significant and growing clinical problem affecting large patient populations worldwide. There is an urgent need for novel scientific and clinical approaches to improve early identification, classification, and treatment of this form of CKD. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.