Monoclonal B-cell lymphocytosis with renal involvement

Area of Science:

• Nephrology
• Hematology
• Oncology

Background:

• Chronic lymphocytic leukemia (CLL) is a common B-cell malignancy.
• Kidney involvement in CLL can manifest in various ways, including acute kidney injury (AKI).
• Monoclonal B-cell lymphocytosis (MBL) is a precursor condition to CLL.

Observation:

• A 70-year-old man presented with AKI and kidney biopsy revealed diffuse interstitial infiltration of CLL phenotype B-cells.
• Peripheral blood studies showed normal lymphocyte counts, no lymphadenopathy, or hepatosplenomegaly.
• Flow cytometry confirmed a clonal B-cell population with a CLL phenotype.

Findings:

• The patient's presentation was initially classified as MBL due to the absence of overt CLL markers in the blood.
• Renal function improved significantly following steroid therapy.
• The patient subsequently developed overt CLL with significant lymphocytosis two years after the initial presentation.

Implications:

• This case highlights that kidney infiltration by CLL B-cells can be an early manifestation of the disease, preceding overt lymphocytosis.
• It underscores the importance of considering B-cell malignancies in the differential diagnosis of AKI, even in the absence of typical CLL signs.
• The findings suggest that MBL with renal involvement may represent a distinct clinical entity requiring careful monitoring and potentially early intervention.