Unusual clonal evolution involving 5q in a case of myelodysplastic syndrome with deletion 5q 31 treated with lenalidomide.

Lenalidomide is a very active drug in myelodysplastic syndrome with del (5q). We report such a patient treated with this drug who developed unusual complex cytogenetic abnormalities, which were elucidated by multi-FISH and FISH analysis as jumping translocations involving the long arm of chromosome 5, that resulted in an increase of 5q copies. This unusual findings is discussed in the context of resistance to lenalidomide observed in this patient.