Clinical and immunopathologic features of idiopathic cutaneous immunoglobulin M/G vasculitis versus idiopathic skin-limited immunoglobulin A vasculitis

A dermatologic addendum to the 2012 Revised International Chapel Hill Consensus Conference recently turned the spotlights on cutaneous small vessel vasculitis as a distinct entity differing from systemic vasculitides with regard to clinicopathologic and laboratory features.A provisional entity named cutaneous immunoglobulin (Ig) M/IgG vasculitis (c-IgM/IgGV), involving postcapillary venules and histologically characterized by a leukocytoclastic pattern, has been introduced. Its clinical differences with the most common skin-limited small vessel leukocytoclastic vasculitis, skin-limited IgA vasculitis (sl-IgAV), need to be elucidated. The objectives of the study were (1) to compare the initial clinical features between these 2 subtypes of skin-limited vasculitis, (2) to compare the outcomes regarding response to treatment and frequency of relapses, and (3) to choose a treatment—a systemic treatment versus a topical one—according to the extension and severity of skin lesions. The data of 41 patients with c-IgM/IgGV and 14 with sl-IgAV were collected. When the initial clinical pattern was assessed, hemorrhagic blisters were observed more frequently in sl-IgAV (n = 6/14; 42.9%) than in c-IgM/IgGV (n = 2/41; 4.9%), with a significant difference ( P = .002). Thirty-two (78%) patients with c-IgM/IgGV and 10 (71.4%) with sl-IgAV received systemic treatments. In patients receiving systemic treatment, CR was achieved in most cases of both c-IgM/IgGV (n = 27/32; 84.4%) and sl-IgAV (n = 7/10; 30%), whereas PR was achieved in 5 of 32 (15.6%) c-IgM/IgG and in 3 of 10 (30%) sl-IgAV patients. The mean latency time between onset of vasculitis and achievement of CR in patients receiving systemic treatment was significantly higher in sl-IgAV than in c-IgM/IgGV (12.9 vs. 9.5 months, respectively; P = .01). Single-episode cases were predominant in both groups, with a single clinical episode of cutaneous vasculitis being reported in 31 of 44 (75.6%) c-IgM/IgGV and 9 of 14 (64.3%) sl-IgAV patients and a chronic-relapsing course, with 1 or more flares being observed in 10 (24.4%) c-IgM/IgGV and 5 (35.7%) sl-IgAV patients. Extracutaneous involvement was not found in any patient.