Perianal Streptococcal Dermatitis

Etiology

Perianal streptococcal dermatitis (PSD) is a slight misnomer. The term dermatitis is used to describe an irritated and inflamed epidermis. While an irritated epidermis is observable with PSD, the disease is actually most commonly caused by the infection of group A beta-hemolytic streptococci (GABHS). Therefore, PSD is more correctly a variant of cellulitis rather than dermatitis.[1][4]

Epidemiology

The most common age group affected by perianal streptococcal dermatitis are patients between the ages of 6 months and 10 years old. Males are more commonly affected than females with a ratio between 3 to 1 and 2 to 1. Interestingly, patients are more commonly affected in the winter and spring months. While perianal streptococcal dermatitis is typically thought to be a pediatric disease, there have been case reports in adults.[1][4]

Pathophysiology

Perianal streptococcal dermatitis classifies as cellulitis most commonly caused by GABHS. There are multiple hypotheses about the mode of infection of the perineum by GABHS. One hypothesis proposes the autoinoculation of the perineal tissues by digital contact with the oral cavity, nasal cavity, and perineum. Patients transfer the bacteria to the perineum either by direct digital contact or by swallowing the bacteria. This hypothesis garners support from the fact that 92% of PSD diagnoses had concomitant pharyngeal GABHS. There is also a belief that fomites could play a role in the transmission of GABHS to cause PSD. Previous studies have found there is a higher occurrence within families and daycare centers. Some attribute the higher occurrence rates to shared surfaces such as toilet seats or bathtubs.[1]

History and Physical

A complete history and physical exam are integral to the accurate and timely diagnosis of perianal streptococcal dermatitis. History from the pediatric patient needs includes the parents. Spending time to conduct a precise history and physical exam will lead the physician to a relatively straightforward diagnosis. Clinicians should have a high index of suspicion for the diagnosis of PSD with any child who has perineal pain and changes in bowel habits. 

Typical symptoms of perianal streptococcal dermatitis include:

• Perineal pain
• Pain with defecation leading to constipation
• Pruritus
• Blood in stool
• Purulent Exudate
• Lack of systemic symptoms

For the diagnosis of PSD, the anus, perineum, and genitalia require examination. PSD classically presents with varying degrees of perianal erythema with well-defined margins. Superficial erosions, anal fissures, excoriations, and purulent discharge may also be present. Once the clinician considers a diagnosis of PSD, definitive tests are necessary.[2][1][3][5]

Evaluation

For a definitive diagnosis of perianal streptococcal dermatitis, bacterial swabs are necessary from the affected areas; ideally of the exudate. The swabs will be sent for culture to confirm the growth of GABHS.[1] Blood tests such as anti-streptolysin O antibodies and anti-streptokinase titers have been deemed unreliable to diagnose PSD.[6] Finally, a urinalysis should be obtained to monitor for post-streptococcal glomerulonephritis during follow-up appointments.[1]

Treatment / Management

After making the diagnosis of perianal streptococcal dermatitis, treatment is relatively straightforward. In minor cases of the disease, some sources recommend treating PSD with topical antimicrobials. However, oral antibiotics are the recommended first-line treatment of the disease. The most successful treatment regimens utilize a combination of systemic and topical antibiotics. Systemic antibiotics include penicillin V, erythromycin, azithromycin, clarithromycin, clindamycin, penicillinase-resistant penicillin, or cephalosporins. These oral antibiotics work best in conjunction with a topical antiseptic such as chlorhexidine, or an antibiotic such as mupirocin. Treatment duration is for 14 to 21 days, and perianal swabs and culture should be taken to ensure eradication of the bacteria.[1][7]

Differential Diagnosis

The following differential diagnoses merit consideration[1][8]:

• Irritant dermatitis - heavy wiping or manipulation
• Candidiasis
• Seborrheic dermatitis
• Atopic dermatitis
• Psoriasis
• Allergic contact dermatitis
• Pinworm infection
• Inflammatory bowel disease
• Histiocytosis
• Sexual abuse

Prognosis

With proper antibiotic use, perianal streptococcal dermatitis usually resolves within 14 to 21 days. However, there is a chance for recurrence due to children's poor hygiene and habitual behaviors.[9] Pediatric patients and their parents need to be counseled on proper hand hygiene and breaking the process of autoinoculation.

Complications

Prolonged discomfort due to delayed diagnosis and treatment is the leading complication of perianal streptococcal dermatitis. There are also extremely rare cases, such as proctitis and abscess formation, caused by concurrent PSD. A prolonged disease course also increases the risk of bacterial transmission to close contacts, particularly siblings and parents. Rheumatic fever is a theoretical complication of PSD. However, there are no case reports published describing this sequela. Cellulitis caused by GABHS, including PSD, can cause post-streptococcal nephritis. Therefore, follow-up urinalysis is essential to monitor kidney function.[1][10]