For patients with nonsevere EGPA, an initial dose of 40–60 mg prednisone is often needed, but I try to reduce more rapidly and quickly establish the minimum dose required to control symptoms, then taper slowly from there. Such regimens end up being highly variable. Prednisone alone is almost always effective for initial treatment, so addition of another immunosuppressive drug is made on the basis of, or in anticipation of the need for, steroid sparing. When to start such a drug is based on guesswork, factoring in the likely two to three months to see benefit. In the absence of data, by analogy to GPA and MPA, I consider methotrexate (20–25 mg/week) and azathioprine (2 mg/kg daily) to be equivalent, and mycophenolate (2,000–3,000 mg daily) to also be a reasonable option.
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However, in light of the success of mepolizumab in a randomized trial, and the good safety profile seen so far in that study and in previous studies in asthma, I am inclined to try mepolizumab if the first oral immunosuppressive drug does not provide sufficient benefit. I don’t see any particular reason to use the 300 mg dose approved for EGPA rather than the 100 mg dose previously approved for asthma with eosinophilia, because the latter circumstance is often what keeps patients with EGPA on prednisone chronically. But it is reasonable to start with 300 mg (and consider reducing to 100 mg later) or start with 100 mg (and increase to 300 mg if needed).
Prophylaxis against Pneumocystis jiroveci and attention to bone health are important, and the minimum dose of immune suppression at which it is safe to discontinue Pneumocystis prophylaxis has not been established.
Other approaches to control asthma should still be encouraged in collaboration with a pulmonologist and not abandoned once a patient is diagnosed with EGPA. These approaches include leukotriene inhibitors; after concern was raised that these drugs might cause EGPA in a small percentage of patients with asthma, the later consensus among experts has been that they can unmask it by allowing reduction in chronic glucocorticoid doses. Patients may require surgical removal of nasal polyps if these do not resolve with medications. Attempts to manage neuropathic pain are often required and often unsatisfactory.
I follow eosinophil counts, ESR, and CRP levels regularly, along with ANCA titers in patients previously ANCA positive, and CK and troponin in patients with a history of cardiac involvement. That being said, eosinophil counts, ESR, and CRP perform poorly as biomarkers of active disease (using clinical assessment as the gold standard) once a patient is on glucocorticoids, and this unfortunate finding has been made with promising experimental biomarkers as well.13,14 The value of serial ANCA measurements continues to be debated in GPA and MPA, and their value can’t be more helpful in EGPA than in MPA. I like to think that normal CK and troponin, in contrast, are fully reassuring about absence of ongoing cardiac damage, in the absence of any data.