The encoded chimeric proteins consist of the N-terminal PAX5 DNA-binding paired domain, which is fused to the C-terminal domains of a remarkable heterogeneous group of partner proteins.<h4>Results</h4>Employing fluorescence in situ hybridization and molecular methods PAX5-KIAA1549L was identified as novel fusion gene in a case of pediatric BCP-ALL.<h4>Conclusion</h4>Our report underlines the high diversity of PAX5 fusion partners in BCP-ALL and we describe the second involvement of KIAA1549L in a genetic rearrangement in acute leukemia. The gene discussed is KIAA1549L; the disease is acute lymphoblastic leukemia.