Timing of Syphilitic Alopecia After Infection
Syphilitic alopecia typically becomes noticeable 2-8 weeks after initial infection with Treponema pallidum, coinciding with the onset of secondary syphilis manifestations. 1, 2
Timeline from Infection to Hair Loss
The progression follows a predictable sequence:
Primary infection occurs at the point of inoculation, with the primary chancre appearing after an incubation period of approximately 2-8 weeks 1
Secondary syphilis develops 2-8 weeks after primary inoculation, which is when hair loss becomes clinically apparent 1, 2
This means hair loss typically manifests approximately 4-16 weeks (1-4 months) after the initial exposure, though it most commonly appears during the secondary stage window 1, 2
Clinical Presentation of Syphilitic Alopecia
When hair loss does occur, it presents with characteristic patterns:
The "moth-eaten" pattern is pathognomonic, appearing as irregular, patchy areas of hair loss scattered across the scalp 3, 4, 5
Prevalence ranges from 3-7% in most studies, though one recent study found it in 41.6% of secondary syphilis patients when specifically examined 4, 5
Important Clinical Context
Several factors affect recognition and timing:
Hair loss may be the sole presenting symptom of secondary syphilis, occurring without other classic manifestations like rash or condyloma lata 3
Other secondary syphilis manifestations typically accompany or precede the alopecia, including the characteristic maculopapular rash involving palms and soles, generalized lymphadenopathy, fever, and malaise 2, 6
HIV co-infection may accelerate disease progression, potentially shortening the typical timeline and making clinical lesions more apparent 1, 2
Diagnostic Considerations
The British Association of Dermatologists guidelines specifically list secondary syphilis as a differential diagnosis for alopecia areata, emphasizing the need for serologic testing when the diagnosis is uncertain 7. This is critical because:
Syphilitic alopecia mimics other forms of hair loss including alopecia areata, telogen effluvium, and tinea capitis, leading to potential misdiagnosis 7, 4, 8
Serologic testing confirms the diagnosis, with both nontreponemal and treponemal tests required 2
Dermoscopy shows reduction in terminal hair number in moth-eaten areas, which can aid diagnosis 5
Treatment Response Timeline
Following appropriate treatment:
Hair regrowth occurs within approximately 3 months after benzathine penicillin G administration 3, 8
First-line treatment is benzathine penicillin G 2.4 million units IM as a single dose 1, 8
Key Clinical Pitfall
Maintain high clinical suspicion for syphilis in any patient presenting with unexplained alopecia, particularly those with risk factors for sexually transmitted infections, as hair loss may be the only initial presenting symptom and can easily be misdiagnosed as other more common causes of alopecia 3, 4, 8.