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In this chapter, a customized approach to each primary lesion, using the diagnostic boxes of the wheel of diagnosis and additional algorithmic decision points, will be introduced. The approach is based on the study of the diagnostic determinants of the primary lesions, the number of lesions present, their grouping or configuration, and the distribution they tend to follow, harnessing additional diagnostic pointers from the scalp, hair, nails, and mucous membranes, and from the history. As mentioned in chapter 1, diagnostic determinants include both visual and tactile features. These are revisited in the textbox below and discussed for each primary lesion, where relevant.

Diagnostic Determinants of Primary Lesions

  • Visual

  • Size

  • Color

  • Shape

  • Surface characteristics: contour and scales

  • Border

  • Tactile

  • Depth

  • Consistency

  • Tenderness

The approach to macules, papules, and pustules is presented in its entirety here. For white macules, a supplemental in-depth discussion of various approaches can be found in Chapter 4. For some of the primary lesions, a fuller discussion will be found in Chapters 6, 7, 8, 9, 10. Examples include a comprehensive discussion of the approach to vesicles and bullae in Chapter 7 and a discussion of nodules based on their reaction pattern, either dermal (Chapter 9) or papulosquamous (Chapter 6). For plaques, which can be categorized into many of the reaction patterns, the global overview presented here is supplemented by reaction pattern–specific information in each respective chapter.


Macules may be categorized primarily according to their color. Other diagnostic determinants, such as size or shape of the macule, may also provide useful information (Table 2.1).

TABLE 2.1.Diagnostic Determinants of Macules

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