Renal Impairment at Multiple Myeloma Diagnosis: Clinical Characteristics, Contributing Factors in a Retrospective Cohort

Background: This study aimed to examine the frequency and clinical characteristics of kidney dysfunction at the time of multiple myeloma (MM) diagnosis, focusing on factors associated with MM-related nephropathy, to identify factors associated with renal recovery among patients presenting with impaired kidney function. Methods: This retrospective single-center study included patients diagnosed with MM between 1999 and 2009. Of 204 screened patients, 136 were eligible for analysis after exclusion of cases with incomplete laboratory or imaging data. Kidney dysfunction was defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² at diagnosis. Demographic characteristics, myeloma subtype, International Staging System (ISS) stage and risk category, laboratory parameters, renal ultrasonography findings, and nephrotoxic exposures were evaluated. Renal recovery was assessed in patients with kidney dysfunction at baseline. Results: Kidney dysfunction was present in 24 patients (17.6%) at diagnosis. Compared with those with preserved renal function, these patients had higher rates of light chain myeloma, and higher β2-microglobulin and CRP levels, and greater proteinuria (all p ≤ 0.05). Moreover, patients with kidney dysfunction were more likely to have higher ISS Stage and high-risk ISS classification (p<0.001). Renal ultrasonography abnormalities—including increased cortical echogenicity and reduced kidney size—were significantly more common in the kidney dysfunction group (p < 0.001). Among patients with kidney dysfunction, renal recovery occurred in 9 of 24 (37.5%). Lower baseline creatinine and absence of hemodialysis requirement at diagnosis were associated with higher recovery likelihood, whereas increased cortical echogenicity or reduced kidney size predicted persistent dysfunction. Conclusion: Kidney dysfunction at diagnosis in MM patients is associated with advanced disease stage, and unfavorable laboratory and clinical features. While β2-microglobulin remains a useful prognostic marker, its interpretation in patients with kidney dysfunction should be approached cautiously due to impaired renal clearance. These findings underscore the importance of early recognition and appropriate management of renal impairment in MM.