These lesions are the consequence of a loss of substance that can either be superficial (erosion), allowing full healing, or deep (ulceration), leaving a scar after healing.

Lesions can be primitive, i.e., the loss of substance is not caused by the evolution of a preexisting lesion; the best example of this type of situation is a posttraumatic ulceration. Otherwise, they can be secondary to other lesions that should be looked for and identified, e.g., the rupture of a bulla or a tumor evolving towards ulceration.

Although leg ulcers are commonplace in elderly people, an isolated ulceration located elsewhere on the integument is never trivial. If a clinical diagnosis cannot be established, biopsy becomes mandatory.

Some ulcerations such as in pyoderma gangrenosum or in hypertensive leg ulcer, as well as those resulting from peripheral arterial disease (limb ischemia), are very painful.

Finally, in immunosuppressed individuals, any type of ulceration should be considered as a manifestation of sepsis, until proven otherwise. The causes of these septic ulcerations are numerous, i.e., bacterial, fungal, and viral. The clinical onset can be violent in patients with neutropenia, e.g., in ecthyma gangrenosum caused by Pseudomonas aeruginosa. It can also be insidious, as in certain infections related to atypical mycobacteria. The main causes of leg and mouth ulcers are listed in Boxes 42.1 and 42.2, respectively.