CD79A and hypersensitivity vasculitis: Skin biopsy revealed the presence of a perivascular inflammatory infiltrate in the superficial dermal blood vessels, with nuclear dust and focal fibrinoid necrosis, consistent with leukocytoclastic vasculitis(LCV) (Figure 2C), accompanied by the deposition of IgA on vascular walls detected by direct immunofluorescent staining, a pathognomonic feature of HSP.