ABSTRACT
Objective:To investigate the clinicopathological characteristics of renal light and heavy chain amyloidosis (AHL).Methods:Ten patients with renal AHL diagnosed by renal biopsy in Peking University First Hospital and Institute of Nephrology of Peking University from January 2015 to June 2020 were enrolled. Clinicopathological data of these patients was collected and reviewed.Results:AHL typically affected older patients, with a male/female ratio of 7:3. The clinical manifestations were mainly edema and heavy proteinuria. At the same time, 7/10 of patients presented with nephrotic syndrome, 7/10 presented with microscopic hematuria, and 3/10 presented with renal insufficiency. Laboratory examinations showed monoclonal immunoglobulin in blood and urine in all patients, and IgGλ was the most common one (5/10). Decreased serum complement could be seen in some patients. The ratio of serum free κ light chain and free λ light chain was abnormal in all patients who underwent serum free light chain test. None of the 10 patients met the diagnostic criteria of multiple myeloma. Except for one of the 10 patients who was diagnosed as Waldenstrom's macroglobulinemia, the rest were diagnosed as monoclonal gammopathy of renal significance (MGRS). Bone marrow of 2/6 of patients were positive for amyloid. Cardiac involvement was confirmed in only one patient. Renal biopsy demonstrated amorphous eosinophilic material, which was Congo red positive, was deposited in glomerular mesangial area (10/10), capillary vessels (8/10), renal interstitium (9/10), peritubular capillary walls (9/10) and arterioles (8/10). This material showed apple green birefringence under polarized light. Immunofluorescence showed that single heavy chain and single light chain were positive at the same time, which was consistent with the results of mass spectrometry analysis. Ultrastructural evaluation revealed randomly oriented, non-branching fibrils with a diameter of 8-12 nm.Conclusions:Main clinical manifestations of AHL amyloidosis are edema and massive proteinuria, along with a high incidence of hematuria, a low portion of heart involvement and high frequency of whole molecule of monoclonal immunoglobulin (IgGλ dominant) by serum immunofixation electrophoresis. Renal pathology shows the commonly involved kidney compartments of amyloid deposits are glomerular capillary walls and peritubular capillary walls in patients with AHL amyloidosis.