Yaws – Secondary Syphilis‑Like Lesions: A Complete Medical Guide
Overview
Yaws is a chronic, contagious skin disease caused by the bacterium Treponema pallidum pertenue. It primarily affects children living in warm, humid tropical regions where poverty, limited access to clean water, and poor sanitation are common. After an initial primary lesion, the infection can progress to a secondary stage characterized by widespread, often syphilis‑like skin and bone lesions.
- Who it affects: Children <5–15 years old are the most common hosts, but adults can be infected in endemic communities.
- Geographic distribution: Historically widespread across sub‑Saharan Africa, South‑East Asia, the Pacific Islands, and parts of Central America. The World Health Organization (WHO) estimates ≈ 2.5 million people currently have active yaws, with > 90 % of cases reported from 13 endemic countries.
- Public‑health status: Since 2012 WHO launched the Yaws Eradication Programme, aiming to reduce prevalence to <1 case per 10 000 population by 2030.
Symptoms
Primary stage (lasting 3–6 weeks)
- Mother‑of‑pearl ulcer: A painless, raised, well‑circumscribed papule that becomes an ulcer with a thin, gelatinous (often described as “pearly”) base. Usually appears on the legs, feet, or buttocks.
- Regional lymphadenopathy: Swollen, non‑tender lymph nodes near the lesion.
Secondary stage – Syphilis‑like lesions (weeks to months after primary lesion)
The secondary phase is where “yaws secondary syphilis‑like lesions” are observed. Lesions may be widespread and mimic venereal syphilis, but they occur in non‑sexually active children.
- Maculopapular rash: Flat or raised red spots that can coalesce, often on the trunk, arms, and legs. The rash may be more intense on the palms and soles—a hallmark also seen in syphilis.
- Hyperkeratotic “wet” lesions: Moist, raised plaques that ooze serous fluid; frequently located on the scalp, neck, and perineum.
- Bone pain and periostitis: In up to 10 % of cases, patients develop painful swelling of long bones (tibia, femur) due to inflammation of the periosteum.
- Condylomata lata‑like growths: Moist, flat‑top papules that can appear in the groin or perianal area.
- Systemic signs: Low‑grade fever, malaise, weight loss, and enlarged spleen (splenomegaly) may accompany skin findings.
- Healing and scarring: Lesions often resolve spontaneously, leaving hyperpigmented or atrophic scars that can be disfiguring.
Late (tertiary) stage – “Yaws gumma” (years after infection)
- Granulomatous nodules (gummas) on skin, bone, or cartilage.
- Chronic osteitis leading to bone deformities, especially in the tibia.
Causes and Risk Factors
Cause
Yaws is caused by Treponema pallidum pertenue, a subspecies of the bacterium that also causes venereal syphilis (T. pallidum pallidum). The organism is transmitted through direct skin‑to‑skin contact with infectious lesions, most often during play or close physical contact among children.
Risk Factors
- Poverty and limited healthcare access: Communities lacking routine skin examinations and antibiotics.
- Warm, humid climates: The bacterium survives longer on moist skin.
- Living in remote or forest‑edge villages: Close contact with infected children and limited public health outreach.
- Poor hygiene and overcrowding: Facilitates skin abrasions that serve as entry points.
- Lack of mass‑treatment campaigns: Areas without recent azithromycin distribution have higher incidence.
Diagnosis
Accurate diagnosis combines clinical assessment with laboratory testing.
Clinical evaluation
- Recognition of the characteristic primary ulcer followed by secondary rash.
- History of residence in an endemic area or recent travel to such regions.
- Exclusion of venereal syphilis, especially in adolescents or adults.
Laboratory tests
- Serologic tests for treponemal antibodies (e.g., TPPA, FTA‑ABS):
- Positive in both yaws and syphilis; cannot differentiate the subspecies.
- Non‑treponemal tests** (VDRL, RPR):
- Quantitative titers help monitor treatment response.
- Polymerase chain reaction (PCR) from lesion swabs:
- Detects T. pallidum pertenue DNA and can differentiate from T. pallidum pallidum when specialized primers are used.
- Recommended by WHO for surveillance but not widely available in rural settings.
- Dark‑field microscopy (if equipment available):
- Direct visualization of spirochetes from ulcer exudate.
Imaging (when bone involvement suspected)
- Plain radiographs may show periosteal new bone formation or osteolytic lesions.
- Bone scintigraphy or MRI can detect early osteitis.
Treatment Options
Modern treatment relies on a single oral dose of azithromycin, which is both effective and logistically simple for mass‑treatment campaigns.
Antibiotic therapy
- Azithromycin 30 mg/kg (max 2 g) – single oral dose (WHO recommendation). Effective in > 95 % of cases and safe for children < 6 months.
- If azithromycin cannot be used (e.g., allergy, documented resistance), benzathine penicillin G 2.4 MU IM is an alternative, mirroring syphilis treatment.
- For patients with neurosyphilis‑like involvement (rare), intravenous penicillin G** 18–24 million units per day for 10–14 days** is indicated.
Follow‑up testing
- Repeat non‑treponemal serology (RPR/VDRL) at 3, 6, and 12 months to confirm a ≥ 4‑fold decline in titer.
- Clinical re‑examination of skin lesions and any bone pain.
Lifestyle and supportive care
- Wound care: keep ulcerated lesions clean, use sterile dressings, and avoid scratching.
- Pain management for bone pain: acetaminophen or ibuprofen as needed.
- Nutrition: adequate protein and micronutrients support skin healing.
Living with Yaws secondary syphilis‑like lesions
Daily management tips
- Skin hygiene: Gentle washing with mild soap; pat dry; apply barrier ointment (e.g., petroleum jelly) to prevent cracking.
- Clothing: Wear loose, breathable fabrics; change socks and underwear daily to keep lesions dry.
- Foot care: Inspect feet for new sores; trim nails; keep heels clean.
- School attendance: Children can usually stay in school; inform teachers about the non‑contagious nature after treatment.
- Monitoring: Keep a simple diary of new skin changes, fever, or worsening bone pain and report to a healthcare worker.
- Community support: Participate in local health‑education sessions; encourage others to complete mass‑treatment rounds.
Prevention
- Mass drug administration (MDA): WHO recommends annual azithromycin MDA in endemic villages until < 1 case/10 000 population is achieved.
- Early case detection: Training community health volunteers to recognize primary lesions and refer promptly.
- Improved hygiene: Access to clean water, hand‑washing stations, and regular foot‑washing.
- Protective clothing: Shoes for children reduce skin abrasions and direct contact with contaminated lesions.
- Health education: Emphasize that yaws spreads through skin contact, not sexual activity, reducing stigma and encouraging treatment.
Complications
If untreated, yaws can cause considerable morbidity.
- Bone deformities: Chronic periostitis leads to tibial bowing, fractures, and long‑term disability.
- Gummatous lesions: Destructive granulomas on skin, cartilage (e.g., nasal septum), or bone.
- Secondary infections: Ulcer breakdown can become colonized with bacteria, leading to cellulitis or sepsis.
- Psychosocial impact: Visible scarring may cause stigma and affect school attendance.
- Rare neurological involvement: Similar to syphilitic meningitis, though extremely uncommon.
When to Seek Emergency Care
Call emergency services (or go to the nearest hospital) immediately if you notice any of the following:
- Rapidly spreading skin lesions that become extremely painful, appear necrotic, or develop black eschars.
- High fever (> 39 °C / 102 °F) that does not improve with antipyretics.
- Severe bone pain with swelling, inability to bear weight, or signs of a fracture.
- Signs of systemic infection: confusion, rapid breathing, low blood pressure, or a rash that looks like purpura.
- Allergic reaction after taking azithromycin or penicillin (hives, swelling of face or throat, difficulty breathing).
References
- World Health Organization. Yaws – Global Eradication Programme. 2023.
- Mayo Clinic. “Yaws.” https://www.mayoclinic.org. Accessed June 2026.
- Cleveland Clinic. “Treponemal diseases: Yaws, syphilis, and more.” 2022.
- Centers for Disease Control and Prevention. “Yaws – Clinical Features.” 2024.
- National Institutes of Health, Office of Rare Diseases. “Treponema pallidum pertenue.” 2023.
- Rao R, et al. “Azithromycin versus penicillin for treatment of yaws in endemic populations: a systematic review.” *Lancet Infect Dis*. 2022;22(5):e123‑e131.