PV manifests as three different subtypes (2): [i] in mucosal-dominant PV, antibodies are restricted to Dsg3 and induce blisters in deep layers of the oral mucosa; [ii] patients with mucocutaneous PV exhibit reactivity against both Dsg1 and Dsg3 and show involvement of the epidermis in addition to the mucous membranes; [iii] the cutaneous PV type is less frequent and associated with blistering in deep epidermal layers owing to anti-Dsg1 and pathogenically weak anti-Dsg3. The gene discussed is DSG1; the disease is acquired polycythemia vera.