RT Book, Section A1 Burgin, Susan SR Print(0) ID 1175058726 T1 Shape, Configuration, and Grouping of Lesions T2 Guidebook to Dermatologic Diagnosis YR 2021 FD 2021 PB McGraw-Hill Education PP New York, NY SN 9780071738750 LK dermatology.mhmedical.com/content.aspx?aid=1175058726 RD 2024/03/28 AB As we have seen in previous chapters, eruptions may manifest lesions with characteristic individual shapes, or characteristic configuration or arrangement of multiple lesions. These attributes of lesions and eruptions can be harnessed as diagnostic tools. As has been previously mentioned, shape is an inherent property of one individual lesion whereas configuration refers to the scheme or arrangement formed by confluent grouped lesions. Sometimes it is difficult to discern whether any given shape is made up of more than one lesion, and so, for convenience, the differential diagnoses of both shape and configuration are discussed in this chapter. For example, papules may be grouped together to form an annular configuration, as is seen in granuloma annulare. Or, a plaque of lichen planus may assume an annular shape if it is depressed in the center and raised at the periphery. Similarly, a line can be made up of a confluence of lesions (configuration), such as the confluent vesicles seen in poison ivy dermatitis, or of one lesion (a shape), such as in dermographism.