Idiopathic cytopenia of undetermined significance (ICUS) versus low risk MDS: the diagnostic interface.

It may sometimes be difficult to diagnose low risk MDS in patients with mild cytopenia. We report on 10 patients with mild to marked, unexplained cytopenia without definitive signs of a myeloid neoplasm. In two patients, a karyotype-abnormality (trisomy 14; monosomy 7) was detected in a small subset of bone marrow cells. Progression to overt MDS was seen in two patients including the one with monosomy 7. In the remaining cases, no MDS developed in a follow-up of at least 6 months. The phrase "idiopathic cytopenia of undetermined significance (ICUS)", as also suggested by Mufti and co-workers, is proposed and long term follow-up is recommended to assess the evolution.