Immunophenotypic profile and clinical outcome of monoclonal B-cell lymphocytosis in kidney transplantation

Monoclonal B lymphocytosis in a kidney transplant recipient

Monoclonal B lymphocytosis (MBL) is a lymphoproliferative condition characterised by expansion of a B-cell clone in peripheral blood, with an often indolent clinical course. The presence of a B clonal population alone is several hundred times more common in the general population than chronic lymphocytic leukaemia and other non-Hodgkin's lymphoma subtypes, it usually does not represent a malignant condition and it requires follow-up only, without specific treatment. There are few studies describing MBL in solid organ transplant recipients, thus, the concern is raised when enrolling MBL affected subjects in waiting lists. We report the experience of a patient affected by MBL who underwent kidney transplantation, with particular attention to preoperative screening and immunosuppressants impact on post-transplant lymphoproliferative disease risk, to aid clinicians in the evaluation process of transplant candidates affected by similar conditions.

Monoclonal B-cell lymphocytosis

Flow cytometry diagnostic practices can detect very low levels of clonal B cells in the peripheral blood. In the absence of clinical symptoms, cytopenia or organomegaly, the small clones may correspond to monoclonal B-cell leukemia (MBL) diagnosis. Most MBLs harbor a chronic lymphocytic leukemia (CLL) phenotype (e.g., CD5⁺, CD23⁺) and are referred to as CLL-type MBL. The two other types are atypical CLL-type MBL and non-CLL-type MBL. In addition to the phenotypical classification, the clonal B count is a major issue because of the impact on the prognosis and the risk of progression in CLL. It allows for the discrimination of two distinct types: high-count (HC) MBL and low-count (LC)-MBL based on a cutoff value of 0.5 × 10⁹/L clonal B cells. LC MBL appears to be very stable over time and is probably related to immunosenescence. Conversely, HC MBL could be a premalignant state before the occurrence of CLL.