Monoclonal gammopathy of undetermined significance coexisting in patients undergoing kidney transplantation does not adversely influence post-graft clinical outcome

Background: Management of patients with oncohaematological disorders such as monoclonal gammopathy of undetermined significance (MGUS) is a frequent problem in pre-transplant work-up. Insights on disease progression and long-term functional outcomes are still lacking in this setting.Methods: This was a retrospective analysis on all patients with MGUS who underwent kidney transplant (KT) at our centre between 1 January 2000 and 31 December 2017 (cases, n=65). Patients were matched with a control group (KTs with similar characteristics but without history of haematological disease, controls, n=1079). Primary endpoints were graft and patient survival; secondary endpoints were causes of graft failure, patient death, occurrence of allograft rejection, post-transplant neoplasia (not correlated to previous disorder) and/or infectious episodes.Results: The MGUS and control groups had a similar mean age [60 (29-79) versus 55.2 (19.3-79.5) years, respectively] and percentage of males (69.2% versus 64.6%, respectively). Median follow-up time since KT was 3.5years (0-14) in cases and 8.3years (0-14.9) in controls. All MGUS patients underwent KT following extensive multidiscliplinary investigations. No differences were found between cases and controls regarding patient and graft survival or post-transplant complications except for lower incidence of infections (58.7% versus 69.8%, P=0.019) and increased use of mTOR inhbitors (30.3% versus 14.7%, P=0.001) in MGUS. MGUS isotype did not influence graft and patient survival. The absence of difference in patients and graft survival was also confirmed in an adjunctive analysis where MGUS were compared with controls (ratio 1:2) matched for recipient age, gender, number of transplantations and transplant period.Conclusion: Patients with MGUS may undergo KT without significantly increased risks of complications, provided that appropriate diagnostic procedures are carefully followed. Multidiscipline-based studies are crucial for establishing well designed pre- and post-transplant protocols for the best management of patients with coexisting MGUS and end-stage renal disease.