Folliculitis Decalvans (Hidroparenquitis): Causes, Features, and Management

Folliculitis decalvans (historically termed hidroparenquitis) is a rare, chronic, scarring (cicatricial) alopecia characterized by recurrent neutrophilic inflammation of hair follicles leading to permanent destruction.

Clinical Features

• Scalp: Patchy hair loss with peripheral active inflammation.
• Follicular Pustules: Crops around active edges.
• Tufted Folliculitis: Multiple hairs (5–20) emerging from single dilated follicular orifice — pathognomonic.
• Scarring: Shiny, poreless, atrophic skin replaces follicles.
• Symptoms: Pruritus, burning, tenderness, drainage.
• Course: Chronic, relapsing-remitting; slowly progressive over years.

Etiology

• Staphylococcus aureus isolated in most lesions (chronic colonization → biofilm → immune dysregulation).
• Not classic infection; represents aberrant host response to follicular microbiota.
• Genetic susceptibility (HLA associations), immune dysregulation implicated.

Differential Diagnosis

• Dissecting cellulitis (perifolliculitis capitis abscedens et suffodiens)
• Acne keloidalis nuchae
• Lichen planopilaris
• Central centrifugal cicatricial alopecia (CCCA)

Management (Multimodal, No Cure)

• Antistaphylococcal: Long-term oral antibiotics (doxycycline, clindamycin, rifampin combinations).
• Anti-inflammatory: Intralesional corticosteroids, topical potent steroids, calcineurin inhibitors.
• Isotretinoin: Low-dose (0.1–0.3 mg/kg) for sebostatic/anti-inflammatory effect.
• Dapsone: Neutrophilic disease modifier.
• Biologics (Emerging): TNF-α inhibitors (adalimumab), IL-17/IL-23 inhibitors — case reports.
• Surgical: Excision of small stable patches; hair transplant only in burnt-out disease.

Prognosis

Permanent hair loss in affected areas. Goal: arrest progression, reduce symptoms. Early referral to dermatologist with cicatricial alopecia expertise is critical.