This assumption is supported by the clear evidence of a direct pathogenic effect of pemphigus autoantibodies as demonstrated by the occurrence of transient pemphigus in neonates of mothers with PV, the correlation of disease activity with serum levels of anti-Dsg1/3 IgG and various experimental models in vitro and in vivo (2, 15, 20, 33). Here, DSG1 is linked to acquired polycythemia vera.