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INTRODUCTION TO CHAPTER

Identification and classification of a patient's skin lesions are important steps in the diagnosis of any skin disorder.1 The numerous descriptive terms used in dermatology can be overwhelming and at times confusing as there are some variations in the use and meaning of these words in the literature.2 The International League of Dermatology Societies developed a glossary for the description of cutaneous lesions which has helped to standardize terminology for skin findings.3 A few simple terms can be used to describe the cutaneous findings in most skin diseases. Using proper terminology to describe skin findings is essential for both documentation and communication with other clinicians. The effort to use precise descriptive terms also encourages a clinician to look with more care and more closely at a patient's skin lesions. Key terms used in the description of lesions are (1) type of primary lesion, (2) secondary features, (3) color of lesion, (4) shape of the lesion, and (5) arrangement and distribution of the lesions.

TYPES OF PRIMARY SKIN LESIONS

It is important to identify and categorize the primary skin lesion(s). This may be difficult if the lesions are excoriated or if the examination takes place late in the disease process. The lesion may need to be lightly touched or deeply palpated to accurately assess its features. Most diagnostic algorithms for skin disease start with the primary lesion. See Chapter 5 for lists of diseases and their primary skin lesions.

Table 2-1 lists the 10 most common morphological terms for types of skin lesions. These are based on:

  • Diameter of the lesion.

  • Relationship of the lesion to the surface of the skin—is the lesion flat or elevated above the surface of the skin?

  • Composition of the lesion—is it solid or fluid filled?

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Table 2-1. Primary lesions and their morphology.
Terminology Diameter Morphology Example
Macule < 1 cm Flat, level with surface of skin and differs in color from surrounding skin. Vitiligo (Figure 2-1)
Patch >1 cm    
Papule < 1 cm Solid, elevated lesion. Chronic allergic contact dermatitis (Figure 2-2)
Plaque > 1 cm    
Wheal Any size White to pink edematous, smooth, papule, or plaque that lasts less than 24 hours. Urticaria (Figure 2-3)
Nodule > 1 cm Dermal or subcutaneous solid elevated lesion. Amelanotic melanoma (Figure 2-4)
Vesicle < 1 cm Blister containing fluid or blood. Bullous pemphigoid (Figure 2-5)
Bulla > 1 cm    
Pustule < 1cm Cavity filled with pus, may be sterile. Pustular psoriasis (Figure 2-6)
Cyst > 1 cm Cavity filled with pus or keratin. Boil (Figure 2-7)

Figure 2-1.

Macules and patches. Vitiligo on dorsum of hand.

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