Although the initiation of SLE and pemphigus is not yet fully understood, abnormal activation of B cells is demonstrated to play central roles in the development and progression of both SLE and pemphigus with the presence of pathogenic autoantibodies in the periphery of the patients, such as anti-nuclear antibodies (ANA) in SLE3 and anti-desmoglein 3 (Dsg 3)/Dsg 1 autoantibodies in pemphigus4. This evidence concerns the gene BTG3 and pemphigus.