Likely Diagnosis: Folliculitis Decalvans (FD)

Key Clinical Features of Folliculitis Decalvans

• Dermatology 2-Volume Set 5e, p. 3836

Management

First-Line: Antibiotic Combination Therapy (Best Evidence)

• Clindamycin 300 mg twice daily
• Rifampin 300 mg twice daily
• Duration: 8-10 weeks
• This combination may be repeated if disease relapses

• Doxycycline (monotherapy or combination)
• Trimethoprim-sulfamethoxazole (TMP-SMX 160/800 mg/day)
• Azithromycin (shorter remission)
• Long-term tetracyclines (sustained response reported)
• Goldman-Cecil Medicine, p. 1474; Dermatology 5e, p. 3843; Andrews' Diseases of the Skin

Supplemental/Topical Therapy

• Topical corticosteroids - to reduce perifollicular inflammation
• Topical calcineurin inhibitors - supplemental anti-inflammatory
• Intralesional corticosteroids - for localized active areas

Second-Line / Refractory Cases

• Isotretinoin - sometimes effective but evidence remains controversial
• Cyclosporine - immunosuppressive option
• TNF-alpha inhibitors: adalimumab, infliximab (low evidence, biologic option)
• Secukinumab (IL-17 inhibitor)
• Apremilast (PDE4 inhibitor)
• JAK inhibitors - emerging evidence
• Photodynamic therapy
• Laser therapies

A 2025 systematic review of 728 patients (PMID 41146582) found that combination therapy (systemic antibiotics + topical and/or other systemic agents) outperforms antibiotic monotherapy, with biologics and laser therapy playing a growing role.

Practical Approach Summary

1. Confirm diagnosis - swab pustules for bacterial culture/sensitivity (rule out MRSA)
2. Start Clindamycin 300 mg BD + Rifampin 300 mg BD for 10 weeks
3. Add topical potent corticosteroid (e.g. clobetasol) to active margins
4. Trichoscopy at follow-up to assess response
5. Warn patient: this is a chronic relapsing condition; repeat antibiotic courses are often needed, and scarred areas will not regrow hair
6. If no response after two courses, escalate to isotretinoin or dermatology referral for biologic therapy

Differential Diagnoses to Consider

• Dissecting cellulitis of the scalp - painful boggy nodules with draining sinuses, also causes scarring alopecia
• Acne keloidalis nuchae - folliculitis at nape with keloid formation, overlaps in some patients
• Tinea capitis - fungal; look for broken hairs, KOH prep will confirm
• Lichen planopilaris - scarring alopecia without prominent pustules
• Bacterial furunculosis - isolated furunculosis without progressive cicatricial pattern

Note: If pustules are predominantly superficial and non-scarring without the cyclic recurrence pattern described, simple bacterial folliculitis (from S. aureus) is also possible and responds to shorter antibiotic courses (10-14 days).

Folliculitis Decalvans (FD) - Management

Step 1: Initial Workup (Before Treatment)

• Bacterial swab of pustules - culture and sensitivity (to identify S. aureus and guide antibiotic choice, rule out MRSA)
• Intranasal swab - S. aureus nasal carriage is a reservoir for recurrence
• Trichoscopy to assess active vs. burned-out disease
• Scalp biopsy if diagnosis is uncertain

Treatment Algorithm (Based on 2025 EADV Position Statement + Textbooks)

Mild Active Disease (perifollicular erythema, hyperkeratosis, NO pustules or crusts)

• Oral isotretinoin - first-line for mild disease (0.5-1 mg/kg/day)
• Topical potent corticosteroids to active areas
• Add topical antibiotics (mupirocin, fusidic acid)

Moderate-to-Severe Active Disease (active pustules, crusts, expanding alopecia)

• This combination gives the longest period of disease remission of all antibiotic regimens
• Note: rifampin must never be used as monotherapy (promotes resistance)
• Courses may be repeated on relapse

• Doxycycline 100 mg BD (long-term; antineutrophilic + antimicrobial action; long-term use sustains response)
• Minocycline, erythromycin, cephalosporins, TMP-SMX (160/800 mg/day)
• Azithromycin (shorter remission)
• Oral fusidic acid (alone or in combination)
• Oral zinc sulfate (adjunctive)

Topical and Local Therapies (add to all systemic regimens)

• Topical antibiotics: mupirocin, 1.5% fusidic acid, 2% erythromycin
• Antibacterial cleansers / selenium sulfide shampoo
• Intralesional triamcinolone acetonide 10 mg/mL every 4-6 weeks - reduces itching, burning, pain at active margins
• Topical potent corticosteroids (e.g. clobetasol) to active areas
• Intranasal mupirocin - to eradicate S. aureus nasal carriage and reduce recurrence

Refractory / Persistent Disease

Long-Term / Maintenance Strategy

• Many patients need long-term low-dose antibiotics for years (especially doxycycline or tetracyclines) to prevent relapse
• "Treatment extended beyond resolution of active lesions" is recommended to avoid recurrence (2025 EADV position statement)
• Combination therapy (systemic + topical + local) consistently outperforms monotherapy in remission duration

Surgical Options (Inactive Disease Only)

• Hair transplantation - only in patients with proven inactive disease (no active pustules or inflammation for at least 1-2 years)
• Surgical excision of affected areas in localised cases

Patient Counselling Points

1. This is a chronic relapsing condition - long-term management is necessary
2. Scarred areas will NOT regrow hair - goal is to stop further loss
3. Antibiotic courses are frequently repeated on relapse
4. Compliance with topical + systemic treatment simultaneously is important
5. Regular dermatology follow-up with trichoscopy to monitor disease activity