An asymptomatic precursor for chronic lymphocytic leukemia.
Defined by the presence of small, aberrant B-cell clones in the peripheral blood.
Total B-cell count is below the threshold for the diagnosis of CLL, that is less than 5000 mm3 per liter.
Occurs in approximately 4-5% of healthy adults.
Prevalence ranges between 0.1% and 14% (Shim YK et al).
MBL is greater than 100 times more prevalent than CLL.
Risk increases in men and with age.
1 to 2% of individuals with MBL progressed annually to CLL that requires treatment.
Most cases of CLL are preceded by MBL.
Only a small subset of MBL patients progress to CLL.
The absolute B-cell count is strongly associated with progression to CLL, and patients with a low count rarely develop CLL.
Retrospective studies demonstrate essentially all subjects who develop CLL have previously detectable MBL clone.
MBL is a premalignant state for CLL as monoclonal gammopathy of undetermined significance is a precursor of multiple myeloma.
1-2% of individuals with MBL progressed annually to CLL requiring treatment.
MBL occurs in 5% of patients with normal blood counts and 13.9% of patients with lymphocytosis.
Progression to CLL is strongly associated with the absolute B-cell lymphocyte count.
The annual risk of developing progressive lymphocytosis, with clinical MBL is approximately 4%.
Most MBL clonal B cells express immunophenotypes similar to that in CLL: CD5+, CD19+, CD20, CD23+, and surface immunoglobulin (sIg).
There are atypical CLL and non-CLL types of MBL, and together they account for 15 to 30% of all cases of MBL.
More common in families with two or more individuals with CLL.
The prevalence of MBL among first-degree relatives of patients with familial CLL ranges from 12-18%.
May occur more frequently in people living in hazardous waste sites than in those residing in a control location.
Hepatitis C is reportedly a host factor potentially involved in MBL development and was detected in 28.5% of HCV patients evaluated, with the trend towards increased frequency among patients with more advanced disease(Fazi C et al).