Management of Infected Sebaceous Cysts and Abscesses

Clinical Differentiation

• Infected sebaceous cysts contain a cyst wall with cheesy keratinous material and skin flora, where inflammation results from rupture of the cyst wall rather than primary infection, while abscesses are simple collections of pus without a cyst structure, and both require incision and drainage as primary treatment, according to the Infectious Diseases Society of America 1, 2, 3
• Patient with infected sebaceous cyst typically reports a longstanding painless nodule that recently became inflamed, painful, and enlarged, as noted by the Clinical Infectious Diseases journal 2, 3
• A distinct capsule or wall structure can often be felt beneath the skin in infected sebaceous cysts, as described in Clinical Infectious Diseases 3
• Infected sebaceous cysts may have a visible dark central opening on the surface, as reported in Clinical Infectious Diseases 2
• When ruptured or drained, infected sebaceous cysts contain thick white-yellow keratinous debris mixed with pus, rather than pure liquid pus, according to Clinical Infectious Diseases 2, 3
• Inflammation in infected sebaceous cysts occurs as a reaction to cyst wall rupture and extrusion of contents into dermis, not true bacterial infection, as noted in Clinical Infectious Diseases 2, 3
• Abscesses develop over days without pre-existing mass and are purely a collection of pus within dermis and deeper tissues without encapsulation, as described in Clinical Infectious Diseases 2, 3
• Abscesses are typically more uniformly fluctuant throughout and contain liquid pus without keratinous material, according to Clinical Infectious Diseases 2, 3
• Abscesses usually contain normal skin flora, with S. aureus present as single pathogen in only ~25% of cases, as reported in Clinical Infectious Diseases 2

Treatment Approach

• Incision and drainage is the cornerstone treatment for both infected sebaceous cysts and abscesses, as recommended by the Infectious Diseases Society of America 1, 2, 3, 4
• The entire cyst wall should ideally be excised to prevent recurrence in infected sebaceous cysts, though this can be done in the same sitting under appropriate anesthesia, as noted in Clinical Infectious Diseases 2
• For both infected cysts and simple abscesses, antibiotics are generally unnecessary after adequate drainage if erythema extends <5 cm from the lesion, temperature <38.5°C, heart rate <110 beats/minute, WBC count <12,000 cells/µL, and no systemic signs of infection, according to the Infectious Diseases Society of America 1, 2, 4
• Add systemic antibiotics to incision and drainage when temperature ≥38.5°C or systemic inflammatory response syndrome present, heart rate >110 beats/minute, erythema extending >5 cm from margins, severely immunocompromised host, incomplete source control after drainage, or multiple lesions or extensive surrounding cellulitis, as recommended by the Infectious Diseases Society of America 1, 2, 4, 5
• Trimethoprim-sulfamethoxazole, clindamycin, and doxycycline are recommended for MRSA coverage in community-acquired infections, according to the Infectious Diseases Society of America 1, 4, 5
• Antibiotic duration is typically 5-10 days based on clinical response, as noted in Clinical Infectious Diseases 4, 5

Critical Distinction in Culture Recommendations

• Gram stain and culture of pus from inflamed epidermoid cysts are NOT recommended, as they typically contain normal skin flora and inflammation is not primarily infectious, according to the Infectious Diseases Society of America 1
• Gram stain and culture ARE reasonable for abscesses and carbuncles, though treatment without these studies is acceptable in typical cases, as noted in Clinical Infectious Diseases 1

Common Pitfalls to Avoid

• Failing to perform adequate incision and drainage is the most critical error, as antibiotics alone are insufficient for either condition, according to the Infectious Diseases Society of America 1, 4, 5
• Prescribing antibiotics unnecessarily shows no significant benefit when added to adequate drainage in simple cases, as reported in Clinical Infectious Diseases
• Inadequate drainage can lead to treatment failure, and complete evacuation of purulent material and break up of all loculations is essential, according to Clinical Infectious Diseases 2, 4, 5
• Missing systemic signs can lead to unnecessary antibiotic use, and vital signs and extent of erythema should always be checked, as recommended by the Infectious Diseases Society of America 1, 4
• Not considering recurrence can lead to repeated infections, and decolonization strategies including intranasal mupirocin and chlorhexidine washes should be considered for recurrent lesions, according to Clinical Infectious Diseases 4