Renal Heavy Chain and Heavy+Light Chain Amyloidosis: A Report of 17 Cases and Comparison with Renal Light Chain Amyloidosis
Authors: Nasr Samih H. , Said Samar M. , Valeri Anthony M. , Sethi Sanjeev , Cornell Lynn D. , Fidler Mary E. , Gertz Morie Abraham A , Dispenzieri Angela , Buadi Francis K , Vrana Julie A , Theis Jason D , Dogan Ahmet , Leung Nelson 
Published: October 2019

Abstract
Abstract 3992
Little is known about the rare entities of heavy and light chain amyloidosis (AHL) and heavy chain amyloidosis (AH). In this study, we report the renal and hematologic characteristics, pathology, and outcome of 17 patients with renal AH/AHL including 5 with AH (4 IgG and 1 IgA) and 12 with AHL (7 IgGλ, 3 IgAκ, 1 IgAλ, and 1 IgMλ), and compare them with 202 patients with renal AL amyloidosis (AL) diagnosed during the same time period. All cases were diagnosed by kidney biopsy that showed Congo red-positive deposits. Amyloid typing was done by laser microdissection and mass spectrometry (LMD/MS) (12 patients) or by immunofluorescence (5 patients). All patients with renal AH/AHL were Caucasians, with a M:F ratio of 2.4 and a median age at biopsy of 63 years. Compared with patients with renal AL, those with renal AH/AHL had less frequent concurrent cardiac involvement, higher likelihood of having circulating complete monoclonal Ig, lower sensitivity of fat pad biopsy and bone marrow biopsy for detecting amyloid, higher incidence of hematuria, and better patient survival. The hematologic and renal responses to chemotherapy were comparable to renal AL. In 42% of patients, AH/AHL could not have been diagnosed without LMD/MS. In conclusion, renal AH/AHL is an uncommon but under-recognized form of amyloidosis, and its diagnosis is greatly enhanced by the use of LMD/MS for amyloid typing. The accurate histological diagnosis of renal AH/AHL and distinction from AL may have important clinical and prognostic implications.
Table 1. Demographics and hematologic characteristics AH/AHL AL p value No. of patients 17 202 Gender: Male/female 12/5 (71%/29%) 126/76 (62%/38%) 0.61 Age, median (range) 63 (50–77) 62 (36–86) 0.73 Additional organ involvement 8 (47%) 126 (62%) 0.3 Cardiac involvement 3 (18%) 100 (50%) 0.01* % of plasma cells in bone marrow, median (IQR) 8 (5–15) 6 (5–10) 0.82     ≥30 plasma cells 4 (24%) 11/198 (6%) 0.02* Positive SPEP/SIF for paraprotein 15 (88%) 158/200 (79%) 0.53     Presence of whole monoclonal protein on SPEP 14 (82%) 108/200 (54%) 0.04* Positive UPEP/UIF for paraprotein 13/16 (81%) 158/189 (84%) 0.73     Presence of whole monoclonal protein on UPEP 10/16 (63%) 61/189 (32%) 0.03* Abnormal serum FLC ratio (<0.26 or >1.65) 9/12 (75%) 150/188 (80%) 0.71 Markedly abnormal FLC ratio (< 0.125 or > 8) 5/12 (42%) 100/188 (53%) 0.55 Positive bone marrow for amyloid 6/16 (38%) 135/183 (74%) 0.004* Positive fat pad biopsy for amyloid 2/14 (14%) 105/145 (72%) <0.001* IQR, interquartile range.
Table 2. Renal characteristics at kidney biopsy AH/AHL AL p value No. of patients 17 202 24h urine protein in g, median (IQR) 5.1 (3.2–9.0) 6.0 (3.2–10.0) 0.9 Full nephrotic syndrome 9/16 (56%) 132/197 (67%) 0.42 Serum albumin in g/dl, median (IQR) 2.7 (2.2–3.3) 2.5 (1.9–2.9) 0.29 % albuminuria on UPEP, median (IQR) 68 (61–72) 70 (60–76) 0.47 Serum creatinine in mg/dl, median (IQR) 1.4 (1.1–2.1) 1.2 (0.9–1.8) 0.25 Serum creatinine >1.2 mg/dl 10/16 (63%) 92/201 (46%) 0.3 eGFR, median (IQR) 47 (27–67) 58 (36–75) 0.29 Decreased eGFR 10/16 (63%) 103/201 (51%) 0.44 Microscopic hematuria 9/16 (56%) 44/169 (26%) 0.02* IQR, interquartile range.

Disclosures:
No relevant conflicts of interest to declare.