What is the likely diagnosis and treatment for an adult patient presenting with a painful pustule and hard white sebum, resembling an epidermal cyst, with a history of severe acne?

Nodulocystic Acne (Acne Conglobata)

The acne type that presents like an epidermal cyst is nodulocystic acne, characterized by deep inflammatory nodules (also known as cysts) that contain purulent material and can mimic true epidermal cysts. 1

Clinical Distinction from True Epidermal Cysts

The key differentiating features help distinguish nodulocystic acne from true epidermal cysts:

Nodulocystic Acne Characteristics:

• Presents as painful pustules and inflammatory nodules in the context of active acne vulgaris, with surrounding inflammatory papules and pustules 1
• Contains purulent material rather than the thick white-yellow keratinous debris characteristic of true epidermal cysts 2, 3
• Develops acutely over days to weeks as part of active inflammatory acne 4
• Multiple lesions typically present in acne-prone areas (face, chest, back) 1, 4

True Epidermal Cysts:

• Longstanding painless nodule that only recently became inflamed 2
• Contains thick white-yellow keratinous debris (cheesy material) mixed with pus when ruptured 2, 3
• Distinct capsule or wall structure palpable beneath the skin 2
• Visible dark central punctum (opening) often present on the surface 2
• Solitary lesion without surrounding acne lesions 2, 3

Treatment Approach for Nodulocystic Acne

Immediate Management:

• Intralesional corticosteroid injections provide rapid improvement for larger inflammatory nodules at risk of scarring 1, 4
• This adjuvant treatment reduces inflammation and pain quickly 1

Definitive Systemic Therapy:

Isotretinoin is the gold standard treatment for severe nodular acne and should be strongly considered, especially in patients with psychosocial burden or risk of scarring 1, 4

• Daily dosing preferred over intermittent dosing 1
• Monitor only liver function tests and lipids during treatment 1
• Pregnancy prevention is mandatory for persons of pregnancy potential 1
• Population-based studies have not identified increased risk of neuropsychiatric conditions or inflammatory bowel disease 1

Alternative Systemic Options (if isotretinoin contraindicated):

• Oral antibiotics (doxycycline for patients ≥9 years, minocycline, or sarecycline) combined with benzoyl peroxide to prevent bacterial resistance 1, 4
• Hormonal agents for female patients: combined oral contraceptives or spironolactone 1, 4

Topical Adjuncts:

• Topical retinoids to normalize follicular keratinization 1, 5
• Benzoyl peroxide for antimicrobial activity and to prevent antibiotic resistance 1, 4

Critical Pitfalls to Avoid

• Do not treat nodulocystic acne with incision and drainage as you would a true epidermal cyst—this is inflammatory acne requiring systemic therapy 1, 4
• Do not use topical antibiotics as monotherapy—always combine with benzoyl peroxide to prevent bacterial resistance 1, 6
• Do not delay isotretinoin in patients with scarring or significant psychosocial burden, as early aggressive treatment prevents permanent scarring 1, 4
• Routine microbiologic testing is not indicated for acne lesions, as P. acnes requires specialized culture and testing does not affect management 1

When to Consider True Epidermal Cyst

If the patient presents with a solitary, longstanding nodule with recent acute inflammation and thick keratinous material upon drainage, this represents an inflamed epidermal cyst rather than nodulocystic acne 2, 3:

• Treatment is incision and drainage with thorough evacuation of contents 2, 3
• Antibiotics are generally unnecessary after adequate drainage unless erythema extends >5 cm, temperature ≥38.5°C, or systemic signs present 2
• Gram stain and culture are NOT recommended for inflamed epidermal cysts, as they contain normal skin flora and inflammation is not primarily infectious 2