[Group A beta-hemolytic Streptococcus: an unusual etiology of perianal dermatitis in an adult?]

Perianal dermatitis usually occurs in children between 1 and 8 years of age. We report a sixth case in an adult.

A 33 year-old woman complained of perianal itching which quickly extended to the vulva and persisted in spite of anti-hemorrhoid and anti-fungal treatments. After 12 days, she had painful defecation, a well demarcated perianal and vulvar erythema and anal collection. Culture from a perianal swab isolated group A beta-hemolytic Streptococcus (ABHS). After surgical treatment of the collection and a 7 days oral amoxicillin regimen, the patient recovered with no recurrence.

Symptoms of perianal dermatitis are unspecific, leading to delayed diagnosis and underestimated frequency. Symptoms consist in perianal erythema. Swab culture shows ABHS. The mechanism of colonization of perianal area is not well defined. Although treatment with oral penicillin is usually effective, failures and relapses have also been reported. Complications such as deep infection or abcess formation are infrequent. A bacterial swab should be made in patients with persisting perianal erythma.