What is the most likely diagnosis and recommended work‑up and treatment for a patient with six months of extensive hair loss, an itchy scalp, and folliculitis?

Extensive Hair Loss with Itchy Scalp and Folliculitis: Diagnosis and Management

Most Likely Diagnosis

The clinical presentation of six months of extensive hair loss accompanied by itchy scalp and folliculitis most likely represents folliculitis decalvans or another scarring (cicatricial) alopecia, rather than alopecia areata. 1, 2

Critical Diagnostic Distinction

The presence of folliculitis fundamentally changes the differential diagnosis and requires urgent evaluation to prevent permanent hair loss:

• Scarring alopecias (folliculitis decalvans, lichen planopilaris, dissecting cellulitis) present with follicular pustules, inflammation, pain, itching, and progressive permanent hair loss 1, 2
• Alopecia areata typically shows smooth, non-inflamed patches without pustules or folliculitis, and hair follicles remain preserved with potential for regrowth 3, 4
• The six-month duration with ongoing folliculitis suggests an active inflammatory process requiring immediate intervention to prevent irreversible follicular destruction 1, 2

Immediate Diagnostic Work-Up

Clinical Examination Features to Document

• Folliculitis decalvans: Look for follicular papules, pustules, erosions, scaly-crusty lesions at patch margins, and tufted hairs (multiple hair shafts emerging from single follicular opening) 1, 2
• Lichen planopilaris: Identify peripilar erythema, perifollicular scaling, and small patches of baldness 2
• Tinea capitis: Examine for broken hairs, black dots, scaling, and cervical lymphadenopathy 5

Mandatory Laboratory Testing

• Skin biopsy is essential when scarring alopecia is suspected—this cannot be diagnosed on clinical grounds alone and requires histologic confirmation 3, 6
• Fungal culture (KOH preparation and culture) to exclude tinea capitis 3, 5
• Bacterial culture from pustules to identify Staphylococcus aureus (commonly implicated in folliculitis decalvans) 1
• Consider serology for syphilis if clinically indicated 3, 4

Treatment Algorithm

If Scarring Alopecia is Confirmed (Most Likely Given Folliculitis)

Immediate aggressive treatment is mandatory because scarring alopecias cause permanent, irreversible hair loss:

• Combination antibiotic therapy targeting S. aureus is first-line for folliculitis decalvans (typically rifampicin plus clindamycin or doxycycline) 1
• Intralesional corticosteroids (triamcinolone acetonide 5-10 mg/mL) to suppress inflammation at active margins 1, 2
• Potent topical corticosteroids (clobetasol propionate 0.05%) applied twice daily to inflamed areas 7, 4
• Folliculitis is a known side effect of topical corticosteroids, but in scarring alopecia the benefit of controlling inflammation outweighs this risk 7, 4

If Non-Scarring Alopecia (Less Likely Given Folliculitis)

• For alopecia areata with fewer than five patches each less than 3 cm: intralesional triamcinolone acetonide achieves 62% full regrowth 3, 4
• Reassurance alone is appropriate for limited disease of short duration, as 80% achieve spontaneous remission 3, 4

Critical Pitfalls to Avoid

• Delaying biopsy in the presence of folliculitis and hair loss: Scarring alopecias cause permanent follicular destruction, and delayed diagnosis results in irreversible baldness 1, 2
• Assuming all hair loss with inflammation is alopecia areata: Alopecia areata does not present with pustular folliculitis 3, 4
• Using only topical treatments for scarring alopecia: These conditions typically require systemic therapy (antibiotics, oral corticosteroids, or immunosuppressants) 1, 2
• Misinterpreting folliculitis as a side effect rather than the primary disease: In this case, folliculitis is part of the disease process, not a treatment complication 6, 1

Prognosis and Counseling

• Scarring alopecias cause permanent hair loss in affected areas—hair follicles are destroyed and cannot regenerate 1, 2
• Early aggressive treatment can halt progression and preserve remaining follicles, but cannot restore already scarred areas 1, 2
• The psychological impact of permanent hair loss is substantial and requires addressing 4