Effect of monoclonal gammopathy in the progression of acute kidney injury and chronic kidney disease: a retrospective observational study

Background The involvement of monoclonal immunoglobulin (MIg) in renal damage in patients with haematological disorders and renal biopsy-proven monoclonal gammopathy of renal significance is well established. However, no epidemiological studies have been conducted on the effects of MIg on renal function in other patients. We aimed to evaluate the renal prognosis of MIg-positive patients and the effects of MIg on renal function. Methods This retrospective observational study was performed using clinical data from all outpatients and inpatients who underwent MIg measurements at the time of enrolment at Kochi Medical School Hospital between 1 January 2017 and 31 December 2021. The primary outcomes were the occurrence of acute kidney injury (AKI) and a decline of > 30% in the estimated glomerular filtration rate (eGFR). Results Among the 1362 patients, 750 were included in our cohort. The number of MIg-positive and MIg-negative patients was 119 (15.9%) and 631 (84.1%), respectively. In addition, the MIg-positive patients were significantly older than the MIg-negative patients. The survival probability of the MIg-positive group was significantly lower than that of the MIg-negative group during the 2 year observation period. The risk factors for the primary endpoint were positive MIg, female sex, lower eGFR, and lower albumin level. Conclusions Our study showed that the presence of MIg was an independent risk factor for renal damage. Therefore, we suggest that MIg-positive patients require careful follow-up of their renal function, even in the absence of a clear underlying disease, such as multiple myeloma.