IgG/IgA pemphigus in a patient with a history of pemphigus vulgaris: An example of epitope spreading?

We report a case of IgG/IgA pemphigus presenting as pemphigus foliaceus following diagnosis and treatment of classic IgG-mediated pemphigus vulgaris. The dual presentation of IgG and IgA positivity on direct immunofluorescence (DIF) constitutes a rare form of pemphigus with a wide variety of clinicopathologic manifestations. The progression of pemphigus vulgaris is commonly because of epitope spreading. However, the patient's disease was partially refractory to rituximab and showed a change in the DIF with dual staining for IgG and IgA. This indicates that class-switching may have occurred with epitope spreading or that there was autoreactive IgA at the onset of disease below the threshold of detection by DIF. Our case indicates that in progressive autoimmune disease refractory to treatment, re-evaluation of the patient for antibody isotypes absent on initial diagnosis may offer key information in better identifying the cause of progression as well as in directing the necessary treatment.