A good example of systemic vs. skin-limited vasculitis would be IgA vasculitis (IgAV), since many patients with vasculitis which present at dermatology offices have skin-limited IgA: the latter is confirmed by leukocytoclastic vasculitis on histopathology and perivascular IgA deposition on immunofluorescence. The gene discussed is CD79A; the disease is Henoch-Schoenlein purpura.