Clinicopathological Characteristics And Outcome Of Monoclonal Gammopathy Patients

[Introduction]The definition of monoclonal gammopathy(MG)is by the presence in serum of a monoclonal immunoglobulin(MIg)resulting from the clonal proliferation of Ig-producing plasma cells or B lymphocytes.The monoclonal gammopathies are a group of disorders range from a nonmalignant small clonal proliferations to malignant neoplasms of plasma cells or B lymphocytes.The monoclonal Igs or its fragments(light chains and/or heavy chains)are secreted into the blood and subsequently filtered by the glomerulus before entering into urine,where kidney is commonly involved in such haematological condition.Kidney damage secondary to monoclonal immunoglobulin in the absence of hematologic malignancy has been increasingly recognized and is now termed MG of renal significance(MGRS).Chronic kidney disease(CKD)is a leading public health problem worldwide.The global estimated prevalence of CKD is 13.4%(11.7-15.1%).During the past decades,the prevalence of CKD and MG has significantly increased,more likely to be concurrent especially among the elderly.Therefore,it is conceivable that some hospitalized patients with MG also have CKD,but the kidney damage is not associated with MIg.Given the different disease management strategies,it is very important to distinguish MGRS from other types of CKD in these patients.Kidney biopsy is the gold standard for diagnosis.However,there is uncertainty about which patients should undergo kidney biopsy and when this should be performed among nephrologists and hematologists.Information is limited about the clinicopathological features of patients with MG and kidney injury who should undergo kidney biopsy.[Objective]To analysis the clinical characteristics and renal pathological manifestations of patients with monoclonal gammopathy and kidney injury.[Methods]This is a multicenter retrospective cohort conducted in four tertiary hospitals in China.The study population comprised the patients with monoclonal gammopathy admitted from January 1,2013 to December 31,2020.The hospitalization record,the laboratory data,and report of kidney biopsy of all study patients from the electronic hospital information system were collected.The study outcomes included the kidney disease progression and major hemorrhagic complication after kidney biopsy.[Results]We identified 1164 patients with MG and 782(67.2%)had underlying kidney injury.Of 101(12.9%)patients undergone a kidney biopsy,16(15.8%)had malignant neoplasms(15 multiple myeloma,1 smoldering multiple myeloma),43(42.6%)MGRS,42(41.6%)non-MIg related kidney disease.Amyloid nephropathy was the most common finding(n=26,60.5%)in MGRS.Membranous nephropathy(n=16,38.1%)was the most common finding(n=26,60.5%)in non-MIg related kidney disease.Serum creatinine and urine protein levels are effectively predictive factors for the prognosis of patients with monoclonal gammopathy.The risk of kidney disease progression in patients with kidney injury is higher than that in patients without kidney injury.Of two patients who suffered major hemorrhagic complications after kidney biopsy,one underwent blood transfusion and the other underwent intra-arterial embolization.[Conclusion]Among patients with MG and kidney injury,only 12.9%underwent the kidney biopsy and 2(2.0%)of them had major hemorrhagic complication.More than 40%patients with MG and kidney injury are not MIg related kidney disease.Kidney biopsy is safe and essential to maximize the possibility of correct diagnosis for patients with clinically suspected MG related kidney disease.