Numerous diseases cause ulcers of the oral mucosa. Once an ulcer forms, regardless of the disease, it results in discomfort. For that reason, differential diagnosis of oral mucosal ulcers is important to both patients and health care providers. Sometimes ulcers are preceded by blisters, but it is often impossible to determine if a blister was present because blisters in the oral cavity rapidly rupture. Small blisters (2-5 mm) are called vesicles, whereas larger blisters (greater than 5 mm) are called bullae (singular bulla).
In some diseases applying lateral pressure to an area of normal appearing skin or mucosa may cause formation of a blister. This phenomenon is known as a Nikolsky sign. A Nikolsky sign may be present in epidermolysis bullosa, pemphigus, mucous membrane pemphigoid, lichen planus and lupus erythematosus. Not all patients with these diseases demonstrate a Nikolsky sign.
A thorough history should be obtained from patients with vesicular-ulcerative diseases and should include the following questions:
Vesicular-ulcerative-erythematous lesions are categorized based on their cause, if known. Lesions are classified as hereditary, autoimmune, viral, mycotic (candidosis or candidiasis), and idiopathic (unknown cause). Bacteria rarely cause oral ulcers and are not discussed here.