Aetiology and management of acute kidney injury in multiple myeloma

Renal Impairment Detectors: IGFBP-7 and NGAL as Tubular Injury Markers in Multiple Myeloma Patients

Background and Objectives: Urine insulin-like growth factor-binding protein 7 (IGFBP-7), tissue inhibitor of matrix metalloproteinase 2 (TIMP-2), and neutrophil gelatinase-associated lipocalin (NGAL) monomer are novel tubular kidney injury biomarkers. In multiple myeloma (MM), immunoglobulin free light chains (FLCs) play an integral role in renal impairment. This study aimed to investigate the correlation between new biomarkers and acclaimed parameters of renal failure, MM stage, and prognosis. Materials and Methods: The examined parameters included: urinary and serum cystatin-C, IGFBP-7, and TIMP-2, and urinary NGAL monomer in 124 enrolled patients. Results: Urinary and serum IGFBP-7 and urinary NGAL were higher among patients with an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2, and positively correlated with urine light chains. Serum and urine IGFBP-7 and urine NGAL were greater among patients with a higher disease stage. In the whole study group, urinary concentrations of the studied markers were positively correlated with each other. In multiple linear regression, urinary IGFBP-7 and NGAL were associated with lower eGFR, independently of other urinary markers. Conclusions: Urinary IGFBP-7 and NGAL monomer may be useful markers of tubular renal damage in patients with MM. Biomarker-based diagnostics may contribute to earlier treatment that may improve renal outcomes and life expectancy in MM.

Bone Marrow Findings in Renal Patients: A Single Renal Specialist Center Experience

Objective

This study evaluated the importance of bone marrow aspiration and trephine biopsy (BM) for the diagnosis of underlying hematological abnormalities in renal patients.

Methods

This cross-sectional study on BM was carried out between August 2010 and April 2019, in our specialist renal center for various unexplained hematological abnormalities in patients with renal diseases [chronic kidney disease (CKD), end-stage renal disease (ESRD) requiring maintenance hemodialysis (MHD), patients with normal renal function but other nephrology and urology issues like stone disease and nephrotic syndrome].

Results

Out of 176 reported BM examinations, 48 (27.3%) were done on ESRD patients on MHD (CKD-D), and 69 (39.2%) on CKD patients not on MHD (CKD-nD). Fifty-nine (33.5%) BM were done on patients with normal renal function (n-CKD). The indication for BM was pancytopenia 50 (28.4%), unexplained anemia 39 (22.2%), and unexplained thrombocytopenia 43 (24.4%). In 91 (51.7%) patients BM was normal. In 30 (17%) patients multiple myeloma (MM) was diagnosed on BM, out of which 18 (26.1%), nine (18%), three (5.3%) were CKD-nD, CKD-D, and n-CKD patients, respectively. In 11 (6.3%) patients BM was suggestive of myelodysplasia (MD), out of these 11 patients, five (10%) were CKD-D patients.

Conclusion

BM is an underutilized method of diagnosis of hematological abnormalities in renal patients. Our study revealed the importance of BM examination, especially in patients with CKD.

Multiple myeloma presenting as acute tubulointerstitial nephritis

Background

Acute tubulointerstitial nephritis (ATIN) is a very rare paraneoplastic manifestation in patients with multiple myeloma (MM). It is an uncommon pattern of renal disease in such patients.

Case presentation

We report a case of an 82-year-old male who was admitted with acute kidney injury. Renal biopsy showed typical findings of light chain-associated ATIN with scattered inflammatory cells in the interstitium and associated active tubulitis. No other common manifestations of MM were present at the time of presentation, including hypercalcemia, hyperuricemia, proteinuria, bone pain or lytic bone lesions. Subsequent immunoassays revealed significant serum lambda light chain burden and Bence Jones protein in urine. Immunofluorescence demonstrated linear tubular basement membranes with positive staining for lambda light chain (3+). Electron microscopy (EM) further showed interstitial edema and inflammation. All the aforementioned findings are consistent with ATIN and supported the diagnosis of MM.

Conclusions

In conclusion, light chain-associated ATIN should be considered in the differential diagnosis of acute interstitial nephritis. Henceforth, serum free light chains as well as serum and urine protein electrophoresis should be included in the workup of such patients.

Evaluating the Relationship of GDF-15 with Clinical Characteristics, Cardinal Features, and Survival in Multiple Myeloma

Growth differentiation factor 15 (GDF-15), a member of the transforming growth factor-β superfamily, participates in processes associated with myeloma development and its end-organ complications. It plays a significant role in both physiological and abnormal erythropoiesis and regulates iron homeostasis through modulation of hepcidin. It is abnormally secreted in marrow stromal cells of patients with multiple myeloma (MM), which may reflect the tumor microenvironment. We analyzed the associations of serum GDF-15 with clinical characteristics of 73 MM patients (including asymptomatic MM) and the laboratory indices of renal function, anemia, and inflammation. Baseline serum GDF-15 was studied as the predictor of two-year survival. We defined five clinically relevant subgroups of patients (symptomatic MM only, patients with and without remission, patients on chemotherapy, and without treatment). Increased GDF-15 concentrations were associated with more advanced MM stage, anemia, renal impairment (lower glomerular filtration and higher markers of tubular injury), and inflammation. Most of the results were confirmed in the subgroup analysis. Serum cystatin C and urine neutrophil gelatinase-associated lipocalin were associated with GDF-15 independently of other variables. In the studied MM patients, GDF-15 did not significantly predict survival (p = 0.06). Our results suggest that serum GDF-15 reflects myeloma burden and shares a relationship with several markers of prognostic significance, as well as major manifestations.

Multiple myeloma and kidney transplantation: the beginning of a new era

The introduction of several novel therapeutic agents has improved the outcome in multiple myeloma (MM) patients including those with chronic kidney disease, and it is predicted that MM will become a curable disease in a substantial subset of MM patients. While in the past-because of inferior posttransplant outcomes-renal transplantation was not offered to MM patients, recent data suggest that renal transplantation is a viable treatment option in patients treated with modern anti-myeloma induction therapy followed by autologous stem cell transplantation achieving durable complete responses. The article of Shah, Ibrahim, Delaney et al. [Risk of relapse of multiple myeloma following kidney transplantation: a case series report. Clin Kidney J 2018 (in this issue)] in the current issue of Clinical Kidney Journal adds to this evidence and highlights the limitations and outstanding questions concerning renal transplantation in MM patients.