Oral erosions usually precede appearance of skin blisters by several weeks.

Flaccid blisters rupture easily because the roof consists of only a thin portion of upper epidermis and is very fragile. Healing is with brown hyperpigmentation, but without scarring.

Skin biopsy shows intraepidermal bullae or acantholysis (separation of the epidermal cells) and mild to moderate infiltrate of eosinophils.