An understanding of the basic lesions that occur on the skin is essential to the discipline of dermatology. Lesions are divided into the general categories of primary and secondary. Primary lesions are those that are directly associated with the disease process and usually appear early in the course of the disease. Those appearing later are called secondary lesions and may be a result of the ongoing disease process and changes to the primary lesions. Secondary lesions are often the result of manipulation by the patient (rubbing, scratching, etc.) or the result of treatments applied to the skin after the process began. An ulceration could be primary (the disease process) or secondary (result of scratching).
A morphological classification of dermatological lesions is most helpful to the identification of the diseases present.
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