Amyloidosis is characterized by extracellular deposition of misfolded proteins as insoluble fibrils. Most renal amyloidosis cases are Ig light chain, AA, or leukocyte chemotactic factor 2 amyloidosis, but rare hereditary forms can also involve the kidneys. Here, we describe the case of a 61-year-old woman who presented with nephrotic syndrome and renal impairment. Examination of the renal biopsy specimen revealed amyloidosis with predominant involvement of glomeruli and medullary interstitium. Proteomic analysis of Congo red–positive deposits detected large amounts of the Apo-CII protein. DNA sequencing of the APOC2 gene in the patient and one of her children detected a heterozygous c.206A→T transition, causing an E69V missense mutation. We also detected the mutant peptide in the proband’s renal amyloid deposits. Using proteomics, we identified seven additional elderly patients with Apo-CII–rich amyloid deposits, all of whom had kidney involvement and histologically exhibited nodular glomerular involvement. Although prior in vitro studies have shown that Apo-CII can form amyloid fibrils and that certain mutations in this protein promote amyloid fibrillogenesis, there are no reports of this type of amyloidosis in humans. We propose that this study reveals a new form of hereditary amyloidosis (AApoCII) that is derived from the Apo-CII protein and appears to manifest in the elderly and preferentially affect the kidneys.
Monoclonal gammopathy is increasingly recognized as a cause of kidney injury. These renal conditions behave differently than ones without monoclonal gammopathy and require specific treatment. To avoid misdiagnosis, testing for paraprotein should be performed in addition to vasculitis and autoimmune diseases serologies in adults with unexplained AKI or proteinuria. Because the prevalence of monoclonal gammopathy is much more common than glomerular diseases, the nephrotoxicity of the monoclonal protein must be confirmed before cytotoxic therapy is initiated. This can only be done by a kidney biopsy. After a monoclonal gammopathy of renal significant is verified, the evaluation should then focus on the identification of the pathologic clone, because therapy is clone specific. We present this patient to illustrate the clinical presentation of a patient with renal dysfunction and a monoclonal gammopathy. This patient is also used to discuss the diagnostic process in detail when monoclonal gammopathy–associated renal disease is suspected.
International Myeloma Working Group Recommendations for the Diagnosis and Management of Myeloma-Related Renal Impairment
Purpose The aim of the International Myeloma Working Group was to develop practical recommendations for the diagnosis and management of multiple myeloma–related renal impairment (RI). Methods Recommendations were based on published data through December 2015, and were developed using the system developed by the Grading of Recommendation, Assessment, Development, and Evaluation Working Group. Recommendations All patients with myeloma at diagnosis and at disease assessment should have serum creatinine, estimated glomerular filtration rate, and electrolytes measurements as well as free light chain, if available, and urine electrophoresis of a sample from a 24-hour urine collection (grade A). The Chronic Kidney Disease Epidemiology Collaboration, preferably, or the Modification of Diet in Renal Disease formula should be used for the evaluation of estimated glomerular filtration rate in patients with stabilized serum creatinine (grade A). International Myeloma Working Group criteria for renal reversibility should be used (grade B). For the management of RI in patients with multiple myeloma, high fluid intake is indicated along with antimyeloma therapy (grade B). The use of high-cutoff hemodialysis membranes in combination with antimyeloma therapy can be considered (grade B). Bortezomib-based regimens remain the cornerstone of the management of myeloma-related RI (grade A). High-dose dexamethasone should be administered at least for the first month of therapy (grade B). Thalidomide is effective in patients with myeloma with RI, and no dose modifications are needed (grade B). Lenalidomide is effective and safe, mainly in patients with mild to moderate RI (grade B); for patients with severe RI or on dialysis, lenalidomide should be given with close monitoring for hematologic toxicity (grade B) with dose reduction as needed. High-dose therapy with autologous stem cell transplantation (with melphalan 100 mg/m 2 to 140 mg/m 2 ) is feasible in patients with RI (grade C). Carfilzomib can be safely administered to patients with creatinine clearance > 15 mL/min, whereas ixazomib in combination with lenalidomide and dexamethasone can be safely administered to patients with creatinine clearance > 30 mL/min (grade A).
Long‐term outcome of patients with POEMS syndrome: An update of the Mayo Clinic experience