Extreme extreme severe burning tongue after aml salvage chemo

My wife has undergone induction chemo and a stem cell transplant.  The stem cell transplant failed a couple of weeks ago and she received seven days of salvage chemo.  Unfortunately, she now suffers from a burning tongue that is so extremely severe that she cannot eat.  Has anyone heard of this?  The doctors seem to think it is a symptom of the chemo that she received, but I think this is much, much, much more serious than than just a symptom.  Please note that I have looked up burning mouth and burning tingue syndrome but this seems much more extreme.

Thanks in advance,

Sincerely,

Brian