Prevalence and Morphology of Leukocyte Chemotactic Factor 2-Associated Amyloid (ALECT2) in Renal Biopsies
CP Larsen, PD Walker, DT Weiss, A Solomon. Nephropathology Associates, Little Rock, AR; University of Tennessee Graduate School of Medicine, Knoxville, TN
Background: Nephropathologists typically identify the protein nature of renal amyloid deposits immunohistochemically utilizing antisera reactive to amyloidogenic precursors. The majority of amyloid cases can be typed with a simple antibody panel including immunoglobulin light chain (κ or λ) and serum amyloid A. However, in some instances, these reagents do not recognize the congophilic material or yield ambiguous staining results, thus creating a diagnostic dilemma. Chemical analysis of fibrils extracted from just such a 'non-reactive' renal biopsy sample led to the discovery of a previously unknown type of amyloid formed from leukocyte chemotactic factor 2.
Design: Among the 21,598 kidney biopsy specimens sent to our laboratory over the past 8½ years, 285 (1.3%) were found histochemically to contain apple green birefringent congophilic deposits that, by electron microscopy, had the typical ultrastructural features of amyloid. Thirty one of these amyloid cases could not be typed immunohistochemically. In an effort to determine if any of these 31 unclassified amyloid-containing samples were LECT2-related, tandem mass spectrometry was performed.
Results: Seven of the 31 cases were identified as ALECT2 (overall 2.5%); this finding was confirmed immunohistochemically using an antiserum specific for LECT2. Pathologically, the deposits were strongly congophilic and had distinctive morphologic features. These features include extensive interstitial involvement in each and, with 1 exception, marked diffuse, global mesangial expansion and displacement by the congophilic deposits.
Conclusions: The extensive interstitial and glomerular involvement, as well as the failure of the amyloid to be immunostained by conventionally used antisera, may indicate the presence of ALECT2. ALECT2 represents the third most common form of renal amyloidosis in our series.
Category: Kidney (does not include tumors)
Monday, March 22, 2010 1:45 PM
Platform Session: Section H, Monday Afternoon