Perianal Streptococcal Dermatitis

Definition

• Bacterial infection of the perianal skin caused by Streptococcus pyogenes (Group A Streptococcus)

• Primarily affects young children, with rare occurrence in adults

• Presents as a sharply demarcated erythematous rash around the anus

Presentation

• Bright red, well-defined rash around the perianal region

• Symptoms include itching, tenderness, burning, and pain during defaecation

• May be associated with mucoid or purulent discharge and minor bleeding

• Often follows a recent episode of streptococcal pharyngitis or skin infection

• Can be accompanied by perineal discomfort and, in some cases, mild systemic symptoms

Differential Diagnosis

• Pinworms: Rule out with a tape test if perianal itching is prominent

• Candidiasis: Common in infants, characterised by satellite lesions and a red rash

• Irritant dermatitis: Due to soaps, wipes or poor hygiene

• Contact dermatitis: Reaction to topical agents or detergents

• Other bacterial infections: Consider if atypical features are present

Diagnosis

• Perianal swab for bacterial culture and sensitivity (MCS) to confirm Group A Streptococcus

• Clinical examination focusing on the distribution and character of the rash

• Rule out alternative causes such as fungal infection or irritant dermatitis through history and appropriate tests

Management

• Antibiotic Therapy

  • Oral cephalexin at 25 mg/kg up to a maximum of 1 g, administered twice daily for 5–10 days depending on severity

  • In cases of penicillin allergy, consider clindamycin or azithromycin with specialist advice

• Supportive Measures

  • Gentle cleansing of the perianal area with warm water and soap-free cleansers

  • Application of a barrier cream, such as zinc oxide, to protect the skin

• Follow-Up

  • Monitor for symptom resolution and ensure adherence to the prescribed antibiotic regimen

  • Re-evaluate if there is no improvement or if symptoms persist beyond the treatment period

Prevention

• Educate caregivers on the importance of regular handwashing and proper perianal hygiene

• Advise on thorough cleaning after defaecation to minimise residual bacterial contamination

• Treat symptomatic household members with strep infections to prevent recurrence

• Encourage prompt medical review for any new or worsening perianal symptoms

Additional Notes

• Early recognition and treatment are essential to prevent complications such as secondary bacterial infection

• The condition may mimic other perianal dermatoses, so a high index of suspicion is required

• Reinforce that perianal streptococcal dermatitis is usually self-limiting with appropriate antibiotic therapy

• Routine follow-up helps confirm resolution and identify any recurrent or resistant cases promptly