Dermatology and Pruritus Ani

Perianal skin is subject to virtually all of the diseases that affect skin and mucosa. The differential diagnosis of disease in perianal skin is broad (Table 16-1) and includes a variety of diagnoses. These diseases almost never present solely within the perianal area; however, there are common diseases such as psoriasis that may present in the perianal area without obvious ties to other areas of the body unless a careful search is made. Certain diseases have specific causes and well-recognized treatment protocols (e.g., psoriasis, candida, and Bowen’s disease), other diseases have less well-defined causes and all too often where therapy is established it is poorly defined. Recognition of important treatable causes requires a disciplined, organized approach to diagnosis with careful and complete history, physical exam, and the frequent use of biopsy. This chapter’s objective is to lay out a strategy to facilitate accurate diagnosis and successful treatment of perianal and anal skin conditions.