How do I diagnose and treat perforating folliculitis in a patient with pruritic papules that may ulcerate, especially if they have chronic renal failure or poorly controlled diabetes?

Diagnosis and Management of Perforating Folliculitis

Diagnosis

Diagnose perforating folliculitis clinically by identifying pruritic, follicular-based papules with central keratotic plugs, typically on the extensor surfaces of the extremities, and confirm with skin biopsy showing transepidermal elimination of dermal material through the follicular epithelium. 1, 2

Clinical Presentation

• Look for discrete, skin-colored or erythematous follicular papules (2-8 mm) with a central adherent keratotic plug, predominantly on the lower extremities (73.3% of cases), forearms, and thighs 1, 2
• Assess for pruritus (present in 83.3% of patients) and Koebner's phenomenon (present in 37% of cases), where new lesions develop at sites of trauma or scratching 2, 3
• The average duration of lesions before presentation is approximately 7-8 months 2

Histopathologic Confirmation

• Perform a punch biopsy showing a keratotic plug penetrating through the follicular epithelium with transepidermal elimination of dermal debris 1, 2
• The deep (profunda) type shows granulomatous inflammation with destruction of the entire follicular complex and sebaceous gland, which leads to scarring 1

Mandatory Systemic Evaluation

• Screen all patients for diabetes mellitus (present in 56.7% of cases) and chronic renal failure (present in 33.3% of cases), as 63.3% of patients have at least one associated systemic disease 2, 4, 5
• Order fasting glucose, HbA1c, serum creatinine, and BUN in every patient presenting with perforating folliculitis 2, 5
• Consider screening for other systemic conditions including connective tissue diseases (such as antisynthetase syndrome) if diabetes and renal disease are excluded 4

Treatment Approach

Optimize control of underlying systemic disease first—particularly diabetes and chronic renal failure—as this is the most critical intervention, since lesions can resolve spontaneously with stabilization of the underlying condition. 3

Primary Management Strategy

• Aggressively manage diabetes to achieve HbA1c <7% and optimize dialysis parameters in patients with chronic renal failure, as metabolic control directly impacts disease resolution 5, 3
• Apply topical corticosteroids (used in 93.3% of patients) as first-line symptomatic therapy for pruritus and inflammation 2
• Prescribe oral antihistamines (used in 80% of patients) for pruritus control 2

Additional Therapeutic Options

• Consider topical or systemic retinoids for refractory cases, though evidence is limited to case reports 5
• Cryotherapy, laser therapy, or narrow-band UVB phototherapy may be attempted for localized, treatment-resistant lesions 5
• Avoid aggressive surgical intervention, as the deep scarring type can result in permanent scarring and disfigurement 1

Critical Pitfalls to Avoid

• Do not treat perforating folliculitis as a simple infectious folliculitis (such as furuncles caused by S. aureus)—incision and drainage or antibiotics are not indicated and will not address the underlying perforating process 6
• Never assume this is an isolated dermatologic condition—failure to screen for diabetes or renal disease means missing potentially life-threatening systemic illness 2, 5
• Do not confuse with other perforating dermatoses (Kyrle's disease, reactive perforating collagenosis, elastosis perforans serpiginosa), though clinical management is similar and all require systemic evaluation 2, 5

Prognosis and Follow-up

• Lesions may resolve spontaneously with stabilization of renal function or improved glycemic control, so reassess after 3-6 months of optimized systemic therapy 3
• The scarring deep type portends a worse cosmetic outcome and may require more aggressive topical therapy 1
• Monitor for Koebner's phenomenon and counsel patients to avoid trauma, scratching, and tight clothing over affected areas 2, 3