Galactose deficient IgA1 (GD-IgA1) in skin and serum from patients with skin-limited and systemic IgA Vasculitis.

BACKGROUND: IgA-vasculitis (IgAV) encompasses a systemic form involving kidneys, gut, skin or joints, and a skin-limited form. One characteristic feature of systemic IgAV is deposition of galactose-deficient IgA1 (GD-IgA1) in kidneys (as in IgA-nephropathy). The relevance of GD-IgA1 for cutaneous vasculitis is unknown. OBJECTIVE: We investigated if GD-IgA1 is deposited perivascularly in systemic and also skin-limited IgAV, and if its serum levels differ between both forms. METHODS: In a case control study, deposition of GD-IgA1 was analysed immunohistochemically by KM55-antibody in skin biopsies from 12 patients with skin-limited and 4 with systemic IgAV. GD-IgA1-levels were compared by ELISA in sera from 15 patients each with skin-limited and systemic IgAV and from 11 healthy subjects. RESULTS: All biopsies from systemic, but also from skin-limited IgAV revealed perivascular GD-IgA1-deposition. The average GD-IgA1-level in serum was significantly higher in systemic than in skin-limited IgAV, despite overlap between both groups. LIMITATIONS: Although high GD-IgA1-levels may be predictive of systemic IgAV, patient numbers were too low to determine cut-off values for systemic versus skin-limited IgAV. CONCLUSION: While perivascular GD-IgA1-deposition is a prerequisite for systemic and skin-limited IgAV, high GD-IgA1-levels in some patients with systemic IgAV suggest a dose-dependent effect of GD-IgA1 in IgAV.