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Many common diseases such as atopic dermatitis, psoriasis, drug rashes, urticaria, viral exanthems, bug bites, and vitiligo present with lesions in multiple body regions. Less common disorders such as syphilis, erythema multiforme, Stevens–Johnson syndrome/toxic epidermal necrolysis, the immunobullous diseases, cutaneous T-cell lymphomas, and connective tissue disorders also present in multiple body locations.


Skin diseases affecting several anatomic sites simultaneously are listed in Table 37-1. Lesion distribution is frequently a very important clue to the diagnosis. For example, atopic dermatitis typically involves the flexor extremities, specifically the popliteal and antecubital fossae, whereas psoriasis vulgaris usually involves the elbows, knees, and extensor surfaces. It is still unclear why certain diseases have a predilection for specific anatomic locations.

Table 37-1.Differential diagnosis of skin diseases involving multiple body regions.

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