Recurrent Erysipelas: An Important Buttock Dermatosis, in Hindsight

Erysipelas is a superficial bacterial infection of the dermis, typically caused by beta-haemolytic streptococci including Streptococcus pyogenes (group A), S. agalactiae (group B) and S. dysgalactiae (group C/G). The typical site is the lower leg, with the face, arm or surgical wounds affected in a minority of cases. Gluteal erysipelas is uncommon and can be multiply recurrent [1].

An 89-year-old woman presented to hospital with an acute painful eruption on the buttocks which began 48 h prior. The patient had experienced five similar episodes in the same distribution over the past 12 months, each of which had resolved with oral clindamycin over 1–2 weeks. The past medical history included recurrent urinary tract infections and stress incontinence. There was no history of trauma or immobility.

Examination revealed well-demarcated, warm, indurated, blanchable plaques on the bilateral buttocks, with an irregular border and peripheral papules. Superficial linear erosions were present on the medial buttocks (Figure 1). The patient was afebrile and there was no inguinal lymphadenopathy. The differential diagnosis included erysipelas, giant cellulitis-like Sweet syndrome, leukaemia cutis, Wells syndrome, panniculitis (including cold panniculitis, factitial panniculitis or paraffinoma), interstitial granulomatous dermatitis, urticaria and irritant contact dermatitis.

Skin biopsy showed papillary dermal oedema and a mixed perivascular and interstitial inflammatory infiltrate, including neutrophils undergoing karyorrhexis (Figure 2). The white cell count was 5.2 × 10⁹/L (4.0–10.0), CRP 119 mg/L (< 5) and blood cultures negative. Swabs from the erosion showed growth of group C/G streptococcus, sensitive to penicillin. The eruption resolved with intravenous cefazolin followed by oral cefalexin for a total of 14 days. Prophylactic penicillin V 500 mg twice daily was commenced at follow-up, and the patient was referred for consideration of low-dose topical oestrogen for genitourinary syndrome of menopause.

Gluteal erysipelas accounts for fewer than 1% of cases of erysipelas. Besides streptococci, Staphylococcus aureus and Gram-negative bacteria are occasionally responsible. The classical presentation is a circumscribed, fiery-red plaque in a butterfly-like distribution over the buttocks. Lesions pass through violaceous and bruise-like stages as they resolve with antibiotic therapy. Predisposing factors are divided into local (lymphoedema, immobility, trauma, surgery, vaginal or anorectal streptococcal colonisation) and systemic (immunosuppression, obesity, metabolic syndrome, alcohol use disorder) [2-4]. Group B and C/G streptococci have a predilection for the buttocks, with most cases occurring in females, and vaginal colonisation may be the common factor [2]. Multiple recurrences occur in one-third of patients, with cumulative lymphatic injury, impaired clearance of microbes and reduced immune surveillance predisposing to further episodes. If recurrences continue despite remediation of contributory factors, antibiotic prophylaxis (penicillin V or erythromycin) is required [5].

This article meets all ethics statement in medical literature and we have obtained the consent of the patient for publication of her case.

The patient gave her consent for the case publication including photography.

The authors declare no conflicts of interest.