Rituximab-associated neutropenia.

Several recent studies have reported the phenomenon of late-onset neutropenia occurring usually several months following the administration of rituximab or rituximab-based therapies. While it appears that late-onset neutropenia is usually not clinically significant and is self-limited, it is important to recognize its existence given the expanding use of rituximab in both hematologic and nonhematologic disorders. Late-onset neutropenia is intriguing biologically and while its pathogenesis and mechanism are not completely understood, many interesting hypotheses have been proposed to explain its occurrence.