Antineutrophil cytoplasmic antibodies of IgA class in neutrophilic dermatoses with emphasis on erythema elevatum diutinum

Objective: To evaluate the prevalence of IgA and IgG antineutrophil cytoplasmic antibodies (ANCAs) in erythema elevatum diutinum in comparison with 2 other groups of neutrophilic dermatoses: Sweet syndrome and pyoderma gangrenosum. Design: Detection of IgA and IgG ANCAs in the serum of patients with neutrophilic dermatoses and characterization of the previously known antigenic targets. Setting: All serum was analyzed without knowledge of diagnosis in the Immunology Department, Pitie-Salpetriere Hospital, Paris, France. Patients: Ten patients with erythema elevatum diutinum, 10 with Sweet syndrome, 10 with pyoderma gangrenosum, and 10 healthy volunteers. Main Outcome Measures: IgA and IgG ANCAs were sought by indirect immunofluorescence with ethanol and formaldehyde-fixed human neutrophil preparations as the substrate. Enzyme-linked immunosorbent assays were further performed for antigen characterization. Results: IgA ANCAs were observed in 60% and IgG ANCAs in 10 (33%) of the patients. All patients with erythema elevatum diutinum had IgA ANCAs. IgA fluorescence in formaldehyde-fixed neutrophils was restricted to those from patients with erythema elevatum diutinum. Enzyme-linked immunosorbent assays disclosed no single predominant target, and antigens remained largely undetermined in erythema elevatum diutinum. Conclusions: The ANCAs, particularly of IgA class, may prove to be a helpful paraclinical marker in erythema elevatum diutinum and an interesting perspective for understanding the pathophysiology of the disease. The nature of the unidentified targets and the pathogenicity of ANCAs, however, remain to be assessed.