While the studies are far from conclusive, differences in immunoglobulin repertoire have also been observed between individuals with clinical MBL and those with population-screening MBL. CLL is characterized by a biased usage of immunoglobulin heavy chain variable region (IGHV) genes with IGHV1-69, IGHV4-34, IGHV3-07 and IGHV3-23 the most frequently used. The presence or absence of somatic mutations in the IGHV genes in patients with CLL correlates with clinical outcome where individuals with mutated IGHV genes having a longer time to first treatment and improved overall survival.(21, 22) Approximately 55% (range 47–58%) of CLL patients have mutated IGHV genes, although this frequency largely depends on the institution (primary vs tertiary referral centers). The IGHV 1-69 gene is the most frequently utilized gene in unmutated CLL cases, while the IGHV 4-34 gene is the most commonly used gene among patients with mutated CLL.(23) Patients with clinical MBL appear to be predominantly IGHV mutated (77–90%)(18, 19) and have an IGHV repertoire that closely resembles that of mutated CLL with IGHV3-07, IGHV3-23, and IGHV4-34 genes utilized in around half of the cases.(18) While some
