DSG1 and acquired polycythemia vera: Since PV and PF primarily involve IgG4 (34), and other IgG subtypes to a lesser extent, ALBIA Dsg-3 assay was performed in six participants with PV, and modified anti-Dsg-1 Euroimmun ELISA in six participants with PF who received extended efgartigimod treatment in cohorts 3 and 4 and achieved a sustained clinical response (28).