Renal Amyloidosis: A Clinicopathological Study From a Tertiary Care Hospital in Pakistan

Introduction Systemic amyloidosis can affect any organ in the body, but the kidney is the most commonly involved site. It is characterized by the extracellular deposition of insoluble fibrillar proteins. Amyloid deposits can be identified histologically by Congo red stain, which gives apple-green birefringence under polarized light. Typing of renal amyloidosis is done by direct immunofluorescence on frozen tissue. The most common types of amyloidosis seen in renal tissue are amyloid light chain (AL) primary amyloidosis and amyloid A (AA) secondary amyloidosis. Although primary amyloidosis is considered the most common type in western countries, however, in the subcontinent region, secondary amyloidosis is more common. The spectrum of signs and symptoms in renal amyloidosis is variable including isolated proteinuria, nephrotic syndrome, hypertension, hypotension, and renal insufficiency. The present study aims to evaluate the incidence and aetiology of various types of renal amyloidosis, determine their distribution within the kidney, and study various clinicopathological features. Objective The present study aims to evaluate the aetiology and clinicopathological profile of renal amyloidosis, determine its various types, and their distribution within the kidney. Materials and methods This retrospective cross-sectional study was conducted from 1st January 2013 to 31st December 2020 at the Department of Histopathology, Shifa International Hospital (SIH), Islamabad. All renal biopsies diagnosed as renal amyloidosis were included in the study. Data were analysed using SPSS version 23 (IBM Corp., Armonk, NY). Frequency and percentages were calculated for qualitative variables, and mean and standard deviation were calculated for quantitative variables. Results A total of 131 cases were diagnosed with renal amyloidosis during the study period of eight years (from 1st January 2013 to 31st December 2020) at SIH. The age range varied from 17 to 82 years. The mean age of the patients was 45 ± 16.33 years. Out of 131 patients, 82 (62.6%) were males and 49 (37.4%) were females. Amongst them, 72 (54%) cases were diagnosed with secondary AA amyloidosis and 16 (12%) cases were diagnosed with primary AL amyloidosis. The rest of the cases 43 (34%) were of indeterminate type. The associated conditions in secondary amyloidosis were tuberculosis in 41 (57%), rheumatoid arthritis in 16 (22%), ankylosing spondylitis in five (7%), lymphoma in three (4%), diabetes in two (3%), and chronic osteomyelitis, chronic heart disease, hepatitis, and vasculitis in one case each (1.7%). Out of 16 cases reported with AL amyloidosis, 10 cases (62.5%) had a history of multiple myeloma. The most common clinical presentation was nephrotic syndrome followed by subnephrotic proteinuria, renal failure, and hypertension. Conclusion The findings of the present study show underlying etiological factors and clinicopathological characteristics of renal amyloidosis. AA amyloidosis is the most common type of renal amyloidosis in our study and tuberculosis is the most common aetiological factor. AL amyloidosis is less frequent in our population.