B-cell chronic lymphocytic leukemia (B-CLL) is the most frequent adult type of leukemia in theWestern countries. It is characterized by the therapeutically uncontrolled accumulation of functionally incompetent lymphocytes in bone marrow, blood and lymph nodes. The development of the disease is heterogenous with distinctive clinical features and individual evaluation of aggresivity is highly recommended for optimal treatment. For this purpose FISH method of identification of genomic aberrations could be used. At present, the new prognostic criterion is accepted – determination of the mutational status of variable region VH of the immunoglobulin heavy chain. This aspect, comparing tumor B-cell nucleotide sequence homology with a germline, separates CLL into two different subsets with markedly different prognoses. A group with an unmutated VH genes with sequence homology > 98% displays progressive disease in contrast to the second group with mutated VH genes and homology < 98%, which represents slowly progressive disease. In the last few years PCR method has been developed for detection of malignant clonal specific expansion and for VDJ rearrangement. Using specific primers it is possible to amplify, sequence and detect the mutations in VH region. The relationship of the VH mutation status to the genomic aberrations and differential influence of these factors on the pathogenesis and progression of B-CLL are the subject of intensive research. Correlation of mutation status with telomere length and cytosine methylation level has been also observed.

        Key words: chronic lymphocytic leukemia, immunoglobulin heavy chain gene, VDJ subgene rearrangement, VH mutational status, prognostic criterium of the aggresivity CLL