In a post‑menopausal woman with frontal fibrosing alopecia, what does the lone‑hair sign signify and how should it guide treatment?

Lone Hair Sign in Frontal Fibrosing Alopecia

What the Lone Hair Sign Indicates

The "lone hair sign" (also called "lonely hair") in frontal fibrosing alopecia signifies active, progressive disease and should prompt immediate initiation or escalation of immunosuppressive therapy to prevent further irreversible scarring. 1

The lone hair sign represents isolated terminal hairs persisting within the scarred, atrophic band of hairline recession. 1 These solitary hairs stand as remnants in otherwise completely scarred areas where follicular ostia have been destroyed. 1 This finding, along with perifollicular erythema, directly correlates with ongoing inflammatory activity and progressive disease. 1

Clinical Significance for Treatment Decisions

Active Disease Markers

• Perifollicular erythema is the most critical marker of disease activity and has a well-established direct correlation with progressive frontotemporal recession. 1
• The presence of lone hairs indicates incomplete follicular destruction but ongoing inflammatory attack, signaling a window where intervention may preserve remaining follicles. 1
• The Frontal Fibrosing Alopecia Severity Score should be systematically applied during every visit, with particular attention to perifollicular erythema as the primary indicator for treatment intensification. 1

Treatment Algorithm Based on Activity

For active disease (lone hairs + perifollicular erythema present):

1. First-line combination therapy should include:

   • 5-α-reductase inhibitors (finasteride 2.5–5 mg daily or dutasteride 0.5 mg daily) 2
   • Intralesional triamcinolone acetonide 5–10 mg/mL every 4–6 weeks to areas of active inflammation 2, 3
   • Hydroxychloroquine 200–400 mg daily 2, 3

2. If no stabilization after 6–7 months, escalate to methotrexate 15–25 mg once weekly as monotherapy or added to the regimen. 1 In a Duke University retrospective study, methotrexate achieved stabilization in 50% of patients with a mean treatment duration of 16 months. 1

3. Adjunctive topical therapy includes:

   • Topical corticosteroids (clobetasol propionate 0.05%) to inflamed areas 2
   • Topical calcineurin inhibitors (tacrolimus 0.1% ointment) 2, 3
   • Topical minoxidil 5% may be added but does not address the inflammatory process 1

For stabilized disease (no perifollicular erythema, no new recession):

• Continue maintenance therapy at reduced frequency, as spontaneous stabilization can occur but is unpredictable. 1, 3
• Monitor every 3–6 months for reactivation markers (return of erythema, new lone hairs, pruritus). 1

Critical Caveats and Pitfalls

Disease Behavior

• FFA progression is highly variable and unpredictable. One patient may experience 30 mm of hairline recession over 72 months, while another shows no positional change after 15 years. 3
• Spontaneous stabilization occurs in some patients regardless of treatment, making it difficult to attribute improvement to any specific intervention. 1, 3
• No treatment has been proven to reverse scarring or regrow hair in destroyed areas—the goal is strictly disease stabilization to prevent further loss. 2, 1

Treatment Monitoring

• Absence of perifollicular erythema does not guarantee permanent remission. The disease can reactivate after years of quiescence. 1
• Drug withdrawal after apparent stabilization carries risk of reactivation, and most patients are understandably reluctant to discontinue therapy even when stable. 1
• The variable natural history means treatment effects may be overestimated—what appears to be treatment success may simply be the disease entering a quiescent phase. 1, 3

Diagnostic Considerations

• Biopsy is no longer necessary when clinical features are classic (progressive frontotemporal recession, scarred atrophic band, loss of follicular ostia, eyebrow loss). 1
• When biopsy is performed, no pathological criteria currently distinguish FFA from lichen planopilaris—they are considered variants of the same disease process. 1
• FFA predominantly affects postmenopausal Caucasian women but can occur in premenopausal women and occasionally men. 4, 3

Associated Features to Document

• Eyebrow loss (partial or complete) occurs in the majority of patients. 3
• Body hair involvement may be present. 4
• Mucocutaneous lichen planus coexists in approximately 17% of cases (3 of 18 patients in one series). 3
• Facial papules (keratosis pilaris-like) and follicular erythema on cheeks may accompany scalp disease. 3

Practical Management Approach

When you see lone hairs with perifollicular erythema: This is active disease requiring aggressive immunosuppression. Start triple therapy (5-α-reductase inhibitor + hydroxychloroquine + intralesional steroids) immediately. 2, 1, 3

When you see lone hairs without erythema: The disease may be transitioning to quiescence, but maintain current therapy and monitor closely every 3 months for reactivation signs. 1

When the scarred band shows no follicular ostia and no erythema: The disease has likely stabilized, but continue maintenance therapy at reduced intensity given the unpredictable risk of reactivation. 1, 3

The lone hair sign is not merely a descriptive finding—it is a call to action signaling that follicular destruction is ongoing and that the window for preserving remaining hair is closing. 1