Preferential activation of the complement system in the lower epidermis of patients with pemphigus vulgaris

Pemphigus vulgaris (PV) is an immune‐mediated blistering skin disease characterized by acantholysis of the suprabasal epidermis and by IgG autoantibodies targeting a desmosomal component, desmoglein 3. IgG alone has been demonstrated to induce acantholysis in some experimental conditions. The role of the complement system in blister formation in PV remains controversial. We describe four consecutive patients with new‐onset PV. The acantholytic process occurred in the lower epidermis and colocalized with deposition of complement C3 and the membrane attack complex C5b‐9. The colocalization of complement deposition with the acantholytic process in the lower epidermis supports a role for the complement system in blister formation in PV.