When would you consider using G-CSF in patients with rheumatic disease who have received cyclophosphamide?

Our primary concern would be our patients with systemic lupus erythematosus. There are reports of severe flares in SLE patients treated with G-CSF (vasculitis and nephritis; Vasiliu et al, PMID 16832843) and even reports of cardiac arrest (Ragsdale & Hall Zimmerman, PMID 34748466).

Of course, this needs to be balanced in the setting of the neutropenia. If a patient is having an infection related to neutropenia, then G-CSF treatment may be needed as the risk for infection complications most likely...

An interesting question!

The first and arguably most important thing to do is define what, if any, harms or benefits that could arise from using G-CSF. Presumably, in this context, G-CSF is being considered or utilized due to cytopenias, presumably arising from (or being attributed to) the cyclophosphamide.

Cyclophosphamide is a potent suppressor of hematopoiesis, and may indeed result in significant cytopenias, with the attendant consequences of those cytopenias (e.g. infection, bleeding, etc). I...