Monoclonal B-cell lymphocytosis

An asymptomatic precursor for chronic lymphocytic leukemia.

Defined by the presence of small, ab2242ant 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).

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