Useful article, thanks. My understanding/experience is that very high absolute counts of eosinophils e.g. > 5 x10e9 are directly cardiotoxic/neurotoxic and may cause multifocal pneumonitis. In most cases I have seen the eosinophils settle quickly if treated early with steroids, a few need mepolizumab (which I think is best supervised by a specialist respiratory unit). There's probably an overlap with HES here - asthma/rhinitis are too common to be reliable differentiators, particularly if the ANCA levels are borderline. I've no doubt that mepolizumab is a good option for some of these patients with chronically elevated eosinophils but some patients can be weaned off treatment. On the other hand, patients with lower counts and more typical ANCA vasculitic features need more conventional immunosuppression but delaying treatment until a biopsy is possible is not a good idea if there's a marked eosinophilia. It's very hard to know how long to treat patients for, difficult to get trial data due to rarity and heterogeneity.
Useful article, thanks. My understanding/experience is that very high absolute counts of eosinophils e.g. > 5 x10e9 are directly cardiotoxic/neurotoxic and may cause multifocal pneumonitis. In most cases I have seen the eosinophils settle quickly if treated early with steroids, a few need mepolizumab (which I think is best supervised by a specialist respiratory unit). There's probably an overlap with HES here - asthma/rhinitis are too common to be reliable differentiators, particularly if the ANCA levels are borderline. I've no doubt that mepolizumab is a good option for some of these patients with chronically elevated eosinophils but some patients can be weaned off treatment. On the other hand, patients with lower counts and more typical ANCA vasculitic features need more conventional immunosuppression but delaying treatment until a biopsy is possible is not a good idea if there's a marked eosinophilia. It's very hard to know how long to treat patients for, difficult to get trial data due to rarity and heterogeneity.