Biochemical Profile of Renal Amyloidosis in a Latin American Cohort

Background: Two-thirds of patients with immunoglobulin light chain (AL) amyloidosis have renal involvement. The biochemical profile of kidney damage is poorly described.

Methods: A cross-sectional study was conducted involving patients diagnosed with AL amyloidosis and renal involvement between January 1, 2010, and April 30, 2022 at the Hospital Italiano de Buenos Aires. Participants were retrospectively identified from the Institutional Amyloidosis Registry. Patients diagnosed with AL amyloidosis and evidence of renal involvement were included. Individuals with other types of amyloidosis were excluded. The selection process involved a thorough review of medical records and registry data to ensure accurate identification and inclusion of eligible participants.

Results: Seventy-seven patients were included. At diagnosis, 90% of the subjects had proteinuria, with a median of 4.3 g/24 h, 61% had renal failure, and 47% presented nephrotic syndrome. Semi-automated urinary electrophoresis revealed 55% with non-selective and 21% with moderately selective glomerular proteinuria. Urine immunofixation indicated 64% with lambda monoclonal free light chains and 12% with kappa. Serum immunofixation demonstrated 48% with lambda monoclonal type and 25% with lambda IgG. At the time of diagnosis of AL amyloidosis, the median age was 66 years (IQR 53-72) and 49% were men. In addition to kidney involvement, other organs were also affected: heart in 53%, gastrointestinal system in 19%, peripheral nervous system in 16%, and liver in 16% of patients.

Conclusion: Our study provides a biochemical profile in renal amyloidosis due to immunoglobulin light chains in a Latin American population. Proteinuria emerged as the most common finding in this cohort with frequent multiorgan involvement.