Pemphigus vulgaris
Rare autoimmune - autoAbs to desmogleins - stick cells together within epidermis
Blisters on skin and mm - fragile and leave erosions - painful and may interfere with sleep and eating
diagnose with biopsy and direct immunoflourescence (normal skin in Michelles medium) or indirect on serology
Mx - high dose oral steroid to control
prob need low dose steroid to maintain - often with other steroid sparing - eg azathioprine, Cyclophosphamide, dapsone
plasmapheresis can also be used. 
?topical steroid in mouth