A 35-year-old man presents with recurrent oral erosions and painful blisters on the palms and soles for 6 months. Histopathology shows acantholysis with suprabasal clefting and a 'tombstone' appearance of basal cells. Direct immunofluorescence reveals IgG and complement deposits in an intercellular pattern throughout the epidermis. Serum IgG antibodies against desmoglein 1 and desmoglein 3 are both positive. Which of the following is the MOST appropriate next step in management?