Reply to the letter of Dr Merdin

Dr Merdin kindly makes suggestions about the design of our study and asks for more information about the infectious and immunosuppressive history of our monoclonal B‐cell lymphocytosis (MBL) patients with monoclonal B‐cell lymphocytosis (MBL). In our study, we incidentally found the coexistence of five cases of MBL and monoclonal gammopathy of undetermined significance (MGUS) in a cohort of kidney transplant recipients at a median of 15 years after transplantation.1 MBL and MGUS are two pre‐malignant lymphoproliferative disorders of terminally differentiated B cells. Clinically, MBL and MGUS share common features, such as an indolent course, a late‐onset age distribution, a low rate of progression and an increased susceptibility to infections. MBL and MGUS are also the precursor states of two hematologic malignancies: chronic lymphocytic leukemia (CLL) and multiple myeloma (MM), respectively.