Many of the infections affecting the perianal area are covered elsewhere in this text. Perianal streptococcal infection is common during infancy and childhood. Major symptoms include a bright red confluent rash around the anal orifice, which sometimes spreads to involve the entire perineal area. Impetiginous lesions sometimes are obvious, with vesicles and honey-colored crusting.
The anal canal usually is involved. Patients may experience small amounts of red rectal bleeding and considerable pain with defecation. A family history of recent streptococcal disease often is obtained, and the patient sometimes has a simultaneous streptococcal pharyngitis. Culture of the anal canal is indicated in any infant whose red “diaper dermatitis” does not heal with standard therapy. Treatment with oral penicillin is recommended, but local antibiotics are not effective. In resistant culture-proven cases, clindamycin may be used.
Anogenital warts usually result from infection with human papilloma virus types 6 and 11. Other serotypes, including type 2 (ie, the usual cutaneous wart virus), may cause perianal disease. The relationship of this infection to sexual abuse was discussed previously.
Chemical removal using podophyllin is difficult in this area because isolation of the wart is not possible. Surgical removal of warts may be indicated if the involvement is extensive.
Molluscum contagiosum lesions may appear in the perianal area. The typical lesion is painless, small, gray-white, and umbilicated on a slightly erythematous base. Lesions usually are seen elsewhere on the body and most often result from autoinoculation. They may be transmitted by sexual contact. Cheesy squamous debris fills the lesion, and cytoplasmic inclusions can be seen in the expressed cells.
Histiocytosis X can present as an isolated, eczematoid, perianal rash. The presence of petechiae in the rash suggests this diagnosis; biopsy is necessary to confirm the diagnosis. Although rare in childhood, malignant melanoma may develop in the anal skin. Pigmented lesions in this area should be carefully observed and biopsied if they increase in size. Plexiform neurofibromas also may arise in the skin of the perianal area. This lesion also requires biopsy if no other signs of neurofibromatosis are present.
Mark Lane Welton, MD
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