Immunogenetic analysis in CLL. Sequencing of the clonotypic IGHV gene rearrangement identifies whether patients with CLL carry IGHV gene somatic hypermutations (M-CLL) or show few or no somatic hypermutations (U-CLL). By analyzing the IGHV-D-J gene usage and the composition of the CDR3, patients with CLL with stereotyped BcR immunoglobulins can be recognized. Here, exemplified by subset number 2 (IGHV3-21/IGLV3-21), which often shows borderline mutation status and always carries the IGLV3-21^R110 mutation. Finally, the IGLV3-21^R110 mutation, which occurs at the border between the IGLJ and IGLC gene, can be assessed by performing a separate multiplex PCR reaction as that proposed by Syrykh et al.