Renal leukocyte chemotactic factor 2 (ALECT2)-associated amyloidosis in Chinese patients

Background: Leukocyte chemotactic factor 2 (ALECT2) amyloidosis is one of the recently described types of amyloidosis. In this study, we reported the first large case series of renal ALECT2 amyloidosis in Chinese patients.Methods: We studied the prevalence, clinical characteristics, renal pathology, outcome and genetic features among seven patients diagnosed with renal ALECT2 amyloidosis at Peking University First Hospital of China from 2000 to 2018.Results: Seven patients were diagnosed with ALECT2 amyloidosis, representing 1.9% of the renal biopsy-proven amyloidosis cases. The mean age at diagnosis was 68 years without gender preference. The patients mainly manifested with varying impaired kidney function with a mean estimated glomerular filtration rate of 42.7 mL/min/1.73 m² (range 8.0-80.5) and proteinuria at 3.9 g/24 h (range 0.4-11.3). There were four ALECT2 amyloidosis patients with concurrent membranous nephropathy (MN), who presented a higher proteinuria (6.4 ± 4.0 g/24 h vs. 2.0 ± 1.8 g/24 h) and higher frequency of nephrotic syndrome (50% vs. 0) than patients with isolated ALECT2 amyloidosis. Renal biopsy showed strongly congophilic amyloid deposits distributed mainly in the renal cortical interstitium, as well as the glomerular mesangium, the inner layer of glomerular basement membrane (GBM), and vascular walls. Two patients with concurrent ALECT2 amyloidosis and MN showed mild amyloid deposits, which have not been identified as ALECT2 amyloidosis by IHC and LMD/MS methods. All patients were corroborated by immunoelectron microscopy to exhibit the specific location of LECT2 in the amyloid fibrils. Genetic analysis revealed no mutations but homozygosity for the G allele encoding valine at position 40 in the mature protein in all patients. Except for one patient who died 8 years later after he was diagnosed with ALECT2 amyloidosis, the others presented with relatively stable renal function during the mean follow-up period of 12.5 months.Conclusions: ALECT2 amyloidosis was the third most common type of renal amyloidosis in Chinese patients from a single centre. The majority of ALECT2 amyloidosis patients were of Han ethnicity, with a high rate of concurrent MN. The recognition and accurate diagnosis of renal ALECT2 amyloidosis should be considered in Chinese patients.