Perianal streptococcal dermatitis, first described in 1966, is an infectious condition of the skin around the anus mostly in children between 6 months and 10 years of age, although cases in adult have been reported. It is caused by group A beta-hemolitic streptococcus (GABHS) bacteria.

Typically dermatitis presents as a moist well-marginated erythema, bright red in color, extended approximately 2-4 cm circumferentially around  the anus. A scant mucoid or serosanguinous discharge can occur. Perianal itching, pain on passing a bowel motion, constipation are present; stools may be blood-streaked.

Local spread to genitalia (penis and vulva) may occur. 

There are no fever or systemic signs.

As the rash becomes more chronic, the perianal eruption may consist of painful anal fissures,  a discharge of pus and/or blood from the rectum.

Perianal swab culture reveals a growth of  group A beta hemolytic streptococci. Most of children with perianal streptococcal dermatitis have a positive pharyngeal cultures for GABHS, even in absence of oropharyngeal symptoms.

The differential diagnosis of perianal streptococcal dermatitis includes:

• pin worn infection,

• candidiasis,

• irritant dermatitis (such as trauma from heavy wiping),

• histiocytosis,

• seborrheic dermatitis,

• psoriasis,

• diaper dermatitis

• eczema,

• sexual abuse.

The management of the disease consists of amoxicillin (40 mg per kg per day divided into three oral doses daily) and/or topical applications of mupirocin, three times per day for ten days. Other alternative antibiotics are penicillin, macrolides (e.g. erythromycin, azithromycin, clarithromycin, for the  patient allergic to penicillin) or clindamycin phosphate. It is preferred amoxicillin suspension rather than the penicillin suspension because the first tastes better leading to a good compliance in children.

Antibiotic treatment results in dramatic and rapid improvement, often within 24 hours. A prolonged treatment course (14-21 days)  may increase cure rates. Clinical follow-up is necessary because recurrences are common (39% of cases). Relapses respond usually to the same antibiotic.