Exploring AA Amyloidosis: Insights from A Case Series in an Under-Explored Indian Context

Introduction: AA amyloidosis is a systemic protein misfolding disorder characterized by the deposition of serum amyloid A protein, often leading to progressive renal dysfunction. While inflammatory etiologies have become more prominent globally, infection-related causes remain a major contributor in resource-limited settings. Data on the clinicopathological spectrum of renal AA amyloidosis in the Indian population are scarce. Methods: This retrospective cross-sectional study included 18 patients with biopsy-proven renal AA amyloidosis evaluated at a tertiary care center in India between March 2022 and May 2024. Clinical data, laboratory parameters, and renal biopsy findings were collected and analyzed. Results: The cohort was predominantly male (83.3%), with a mean age of 37.2 years (range 17–65). Chronic infections were the leading etiology (77.8%), with tuberculosis being most common (64.3%), followed by hepatitis B/C and HIV coinfections. Autoimmune conditions (Rheumatoid Arthritis, Ankylosing Spondylitis) accounted for 16.7% of cases. All patients presented with proteinuria (mean 3.2 ± 2.5 g/24h), and 38.9% showed hematuria with RBC casts. Severe hypoalbuminemia (<2.5 g/dL) was seen in 66.6% of patients and was significantly associated with higher proteinuria (p = 0.0123). Acute kidney injury was present in 33.3% of patients. Renal biopsy confirmed amyloid deposits with Congo red staining and strong SAA positivity on immunohistochemistry. Conclusions: In contrast to global trends, infectious diseases remain the predominant cause of AA amyloidosis in the Indian population. This study highlights the need for heightened clinical vigilance and timely renal biopsy in patients with chronic infections and unexplained proteinuria to improve early diagnosis and management.