Perianal Streptococcal Dermatitis (PSD) is a streptococcal infection occurring in the anal region. It is caused by Group A Streptococcus (GAS), the same bacteria responsible for common strep throat. Although PSD is most frequently diagnosed in children, it can affect individuals of any age. Recognizing this bacterial infection is important because it requires specific antibiotic treatment, unlike a simple rash or fungal irritation.
What is Perianal Streptococcal Dermatitis?
Perianal Streptococcal Dermatitis is a bacterial skin infection involving the area immediately surrounding the anus. The infection is localized to the skin and subcutaneous tissue, sometimes referred to as perianal streptococcal cellulitis. The affected area is the skin of the perineum, which can sometimes extend to involve the genital area, such as the vulva or penis. While it is a skin infection, it can penetrate the deeper layers of the skin, requiring medical intervention.
Recognizing the Physical Signs
The clinical presentation of PSD is characterized by a distinctive rash. The skin around the anus appears intensely red and has a sharply defined, “beefy-red” border, typically extending about two centimeters from the anal opening. The infection causes significant discomfort, including intense itching and pain in the perianal area. This pain is frequently exacerbated by bowel movements, which can cause children to withhold stool, potentially leading to secondary constipation. The irritation can also cause fissures, which are small, painful tears sometimes resulting in blood streaks visible on the stool or toilet paper.
This bacterial infection must be differentiated from other causes of perianal redness, such as candidiasis or simple irritant diaper dermatitis. Unlike a common diaper rash, the strep infection is typically more intensely red and has a well-demarcated edge. Furthermore, a strep infection will not improve with topical antifungal or barrier creams alone.
Transmission Routes and Medical Testing
Transmission Routes
Group A Streptococcus is highly contagious, especially within household settings. The primary method of acquiring the infection is thought to be through the fecal-oral route, where bacteria are transferred from the infected anal region. Another common pathway is auto-inoculation, occurring when an individual with strep throat or a skin infection like impetigo transfers the bacteria to the perianal area via their hands. The bacteria can also be spread through close personal contact or by sharing contaminated items like bath towels or toys. In many cases, a child may be an asymptomatic carrier of GABHS in their throat, which then leads to the development of perianal dermatitis.
Medical Testing
Diagnosis requires a medical evaluation and confirmation of the Streptococcus bacteria. A healthcare professional will perform a physical examination and take a swab of the affected perianal area. This swab can be used for a rapid strep test, similar to the one used for strep throat, which provides quick results. A more definitive method is sending the swab for a bacterial culture to confirm the growth of Group A beta-hemolytic Streptococcus. Accurate diagnosis is necessary to ensure correct treatment, as misdiagnosis is common due to visual similarity to other rashes.
Treatment and Preventing Future Infection
Treatment
Treatment requires specific oral antibiotics to eradicate the bacterial infection, typically penicillin or amoxicillin. Amoxicillin is often preferred in pediatric cases because its liquid formulation is better tolerated by children. The duration of antibiotic therapy is usually around 10 days, though some regimens may extend up to 21 days to ensure complete clearance. It is important that the full course of prescribed medication is completed, even if symptoms improve rapidly. Failing to complete the course increases the risk of the infection recurring.
Preventing Future Infection
Preventing future infection and limiting spread relies heavily on meticulous hygiene practices. Thorough and frequent handwashing is necessary for the affected individual and all caregivers. It is recommended to use dedicated towels and washcloths for the infected person and to avoid sharing bath water. If other family members, especially siblings, show signs of strep infection or test positive, they should also receive appropriate treatment to stop the cycle of transmission.