Monoclonal B-cell lymphocytosis in the population of Slovenian region of Lower Carniola

Summary Introduction Monoclonal B‐cell lymphocytosis (MBL) is a premalignant asymptomatic condition characterized by the presence of a small population of monoclonal B lymphocytes (less than 5 × 109/L) in the venous blood of otherwise healthy individuals. Incidence of MBL is higher among first‐degree relatives of patients with chronic lymphocytic leukemia (CLL) and also increases with age and among men. We compared the incidence of MBL found in the same environment in both an open general population and relatives of CLL patients. Methods Samples were analyzed with 5‐parameter flow cytometry using following monoclonal antibodies: kappa and lambda clonality, CD5, CD19, CD20. We analyzed 216 samples of patients in the Slovenian area of Lower Carniola aged 23–88 years. Fifty‐four patients who came from families where CLL is present were compared by age and gender to 162 healthy individuals from the general population of the same region. Results We found 10 cases of MBL (4.6%). In 9.4% of younger (≤ 50 years) first‐degree relatives of CLL patients with immunophenotypic characteristics of atypical MBL, we observed a prevailingly normal κ to λ ratio. The difference in incidence of MBL cases between relatives and the general population decreases with age. Conclusion MBL in Slovenia can be coincidentally found with a similar frequency to previously studied populations of other parts of Europe. We found, however, a higher incidence of atypical MBL among first‐degree relatives.