medwireNews: Patients who have granulomatosis with polyangiitis (GPA) and high blood eosinophil levels at diagnosis are more likely to have severe disease and skin and neurological involvement than those with lower levels, French study findings indicate.
These data suggest that blood eosinophil levels at diagnosis could identify “GPA subsets with different phenotypes,” which approach eosinophilic (E)GPA features “for some aspects,” say Benjamin Terrier (Hôpital Cochin, Paris, France) and colleagues.
They write in Rheumatology: “Whether these subsets of patients could benefit of different treatment strategies remains to be investigated.”
The study findings are based on an analysis of data from 354 patients with GPA who were included in the French Vasculitis Study Group Database. When diagnosed, 25.4% of the patients had blood eosinophil levels of at least 500/mm3. Specifically, 17.5% of patients had mild-to-moderate hypereosinophilia (HE) with levels between 500 and 1500/mm3 and 7.9% had severe HE with levels exceeding 1500/mm3.
Terrier and co-authors report that patients with increased blood eosinophil counts above 500/mm3 “displayed a few peculiar features,” compared with patients with normal eosinophil levels (<500/mm3).
These features included a significantly higher mean disease activity at baseline, with corresponding Birmingham Vasculitis Activity Scores of 21.19 versus 18.37, and significantly higher rates of cutaneous manifestations (48.9 vs 33.3%) and peripheral neuropathy (32.2 vs 17.0%) with sensory (24.4 vs 4.4%) and motor (20.0 vs 6.1%) involvement.
Thus the “GPA patients with HE, although free from asthma, displayed some similarities with EGPA, such as a higher proportion of skin involvement and peripheral neuropathy,” the team notes.
The patients with severe HE also had a significantly higher rate of renal failure (>30% serum creatinine increase) than those with mild-to-moderate HE or normal eosinophil levels (53.6 vs 25.8 and 26.1%).
Over a median follow-up of 3.95 years, cutaneous and neurologic flares occurred more frequently among patients with mild-to-moderate and severe HE than those with normal eosinophil levels, at respective rates of 2.8 and 3.6 versus 1.2 flares per 100 patient–years and 3.5 and 5.5 versus 1.9 flares per 100 patient–years. But there was no significant difference in overall relapse rates among the three groups, with 16.9, 19.3, and 16.4 flares per 100 patient–years, respectively.
The researchers propose that “mechanisms supporting damage in GPA with increased [eosinophils] could be related to eosinophil-related tissue damage, explaining some shared features with EGPA, especially the skin and neurological involvement.”
Damage burden was comparable across the patient groups at the last visit, regardless of blood eosinophil level at baseline, but peripheral neuropathy as damage was more common among those with severe HE than those with lower eosinophil levels.
The study investigators say that “[t]he present study adds another piece to the ‘puzzle’ of non-asthmatic hypereosinophilic vasculitides,” with one patient with severe HE being antineutrophil cytoplasmic antibody-negative and meeting a newly proposed “set of criteria for a new entity named eosinophilic vasculitis.”
Terrier et al conclude that “despite the rarity of this patient’s phenotype, our finding further highlights the need to think about GPA in the differential diagnosis of these forms.”
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