Clinicopathological characteristics and prognostic factors in renal amyloidosis: a 10-year Australian tertiary centre experience.

Renal amyloidosis is an important cause of kidney injury that is often associated with significant morbidity and mortality. In this study, we aim to characterise the clinicopathological patterns and identify potential prognostic factors in renal amyloidosis at an Australian tertiary referral centre over a decade. A total of 63 biopsy-diagnosed cases of renal amyloidosis from 2011 to 2021 were retrospectively reviewed. Cases were initially subtyped by immunofluorescence and immunohistochemistry. Mass spectrometry was performed when rare subtypes were suspected. Histological characteristics were correlated with clinical parameters at the time of biopsy. The primary outcome was severe renal impairment (SRI), defined as an estimated glomerular filtration rate (eGFR) <10 mL/min/1.73 m2 or commencement of renal replacement therapy. Amyloid light chain (AL) amyloidosis was the most common subtype (79%), followed by amyloid A (AA) (11%), and the rare subtypes included amyloid leukocyte cell-derived chemotactic factor-2 (3.2%); amyloid transthyretin wild-type (1.6%); amyloid apolipoprotein C-II (1.6%); amyloid fibrinogen (1.6%); and amyloid gelsolin amyloidosis (1.6%). Patients with AA amyloidosis were younger than those with other subtypes. The classic histological patterns of common and rare amyloid subtypes, as described in the literature, were replicated in our cohort. Interstitial fibrosis and tubular atrophy had a strong correlation with baseline eGFR and were important prognostic factors for SRI. Nephrotic-range proteinuria showed a trend towards SRI, but amyloid subtype (AL vs AA vs other) did not stratify outcome. Most AL amyloidosis cases (69%) were confirmed to be monoclonal gammopathy of undetermined significance, with a smaller proportion showing an underlying haematological malignancy. All patients with AA subtype had an underlying chronic inflammatory disease condition. We demonstrate classic histopathological features of common and rare subtypes of renal amyloidosis in an Australian cohort. Histological markers at biopsy, indicative of chronic renal damage, have value as prognostic factors.