Isochromosome i(3q) and premature chromosome condensation are recurrent findings in chronic B-cell lymphocytosis with binucleated lymphocytes.

Chronic B lymphocytosis with binucleated lymphocytes (LWBL) is a recently described entity. The lymphocytosis is stable over years and atypical binucleated lymphocytes are detected on peripheral blood smears. Further investigation has shown a predominance in females, a polyclonal increase in serum IgM and HLA-DR7 expression in most cases. In almost all cases cytogenetic studies with classical culture conditions have not shown any abnormality. We describe 7 patients with LWBL associated with an abnormal karyotype. An additional i(3q) was found in 6 cases. Premature chromosome condensation (PCC) was detected in all 7 cases. As both abnormalities are rarely present in other benign or malignant proliferations, we suggest a strong correlation between LWBL and i(3q) and/or PCC.