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Yaws – Secondary (Late) Stage: A Complete Medical Guide

Overview

Yaws is a chronic, skin‑to‑skin transmitted infection caused by the bacterium Treponema pallidum subspecies pertenue. It is one of the three treponemal diseases that affect humans (the others are syphilis and pinta). Yaws follows a distinct clinical course with an initial primary (or early) stage, followed by a secondary (late) stage that can appear months to years after the first lesions. The secondary stage is characterized by widespread skin and bone manifestations that may lead to permanent disfigurement if left untreated.

Yaws is almost exclusively a disease of children living in impoverished, tropical, and subtropical regions. The World Health Organization (WHO) estimates that **approximately 84 million people** live in endemic areas, with **250 000–500 000 new cases** reported each year, the majority of which occur in West Africa, Southeast Asia, and the Pacific Islands.<sup>[1]</sup> The disease is largely absent from industrialized nations because of improved sanitation and access to health care.

Symptoms

Typical presentation in the secondary (late) stage

• Skin lesions (papules, nodules, plaques) – Often multiple, ranging from 1 mm to several centimeters, may be flat or raised, and can appear on the trunk, limbs, and face. They are usually painless but can become ulcerated or crusted.
• “Warty” or “gummatous” lesions – Thickened, cauliflower‑like growths that can coalesce into large plaques, especially on the buttocks, thighs, or back of the hands.
• Bone pain and periostitis – Involvement of long bones (tibia, femur) causes aching, swelling, and sometimes palpable “soft spots” where new bone is forming.
• Joint inflammation (arthralgia) – Migratory joint pain without true arthritis, commonly affecting knees and ankles.
• Hyperpigmentation or hypopigmentation – After lesions heal, they may leave dark or light spots that persist for months.
• Scar formation – Deep ulcerated lesions can heal with atrophic or hypertrophic scarring, potentially leading to deformity.
• Secondary bacterial infection – Scratching or trauma to lesions may permit super‑infection with Staphylococcus or Streptococcus species, producing pus, increased pain, and systemic signs.

Less common but reported manifestations

• Palmar‑plantar hyperkeratosis (thickened soles and palms).
• Lagophthalmos or conjunctival scarring when lesions occur near the eye.
• Rare neurological involvement (meningitis) – far more common in syphilis, but isolated case reports exist.

Causes and Risk Factors

Yaws is caused by Treponema pallidum subspecies pertenue, a spirochete that cannot survive long outside the human body. Transmission occurs primarily through direct, non‑sexual skin contact with infectious exudate from active lesions. The bacterium enters via small abrasions or cuts.

Key risk factors

• Age – 85‑90 % of cases occur in children aged 2‑15 years.
• Poverty and limited access to clean water – Overcrowded living conditions increase skin‑to‑skin contact.
• Rural, tropical environments – Warm, humid climates favor bacterial survival on moist skin.
• Occupational exposure – Farming, fishing, or school attendance where children play barefoot and share clothing.
• Lack of community health programs – Absence of mass‑treatment campaigns or health education.

Diagnosis

Accurate diagnosis relies on clinical suspicion combined with laboratory confirmation. Because yaws and syphilis share the same treponemal antigens, serologic tests cannot differentiate them; epidemiologic context is essential.

Diagnostic steps

1. Clinical assessment – Recognition of characteristic lesions, distribution, and patient history (living in an endemic area).
2. Serologic tests
   • Rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL) test – Non‑treponemal tests that become positive after 1‑2 weeks of infection. Titers usually decline after successful treatment.
   • Treponemal tests (TPPA, FTA‑ABS) – Remain positive for life; used to confirm treponemal infection.
3. Dark‑field microscopy or PCR – Direct visualization of spirochetes from lesion exudate or PCR detection of treponemal DNA. These are reference‑level methods and not widely available in remote settings.
4. Radiography – X‑ray of affected bones can reveal periosteal new bone formation, confirming late-stage involvement.

According to the WHO yaws surveillance guidelines, a **positive serology plus typical skin lesions** in a child from an endemic community is sufficient for a presumptive diagnosis and immediate treatment.<sup>[2]</sup>

Treatment Options

Single‑dose therapy with an oral antibiotic is highly effective, even in late disease.

First‑line antimicrobial therapy

• Azithromycin 30 mg/kg orally, single dose (maximum 2 g) – WHO‑recommended since 2012 because of its ease of administration, safety profile, and excellent tissue penetration.<sup>[3]</sup>
• Benzathine penicillin G 50,000 IU/kg intramuscularly (max 2.4 million IU) – single dose – Recommended for pregnant women, infants <6 months, or when azithromycin resistance is suspected.

Management of complications

• Secondary bacterial infection – Oral amoxicillin or clindamycin based on local resistance patterns.
• Severe bone involvement – Analgesics (acetaminophen or ibuprofen) and physiotherapy to preserve joint function.
• Scarring – Referral to dermatology for silicone gels, pressure therapy, or surgical revision after infection resolves.

Follow‑up

Repeat non‑treponemal serology (RPR/VDRL) at 3, 6, and 12 months. A four‑fold decline in titer indicates adequate response. Persistent or rising titers warrant re‑evaluation for reinfection or treatment failure.

Living with Yaws – Secondary Stage

Daily self‑care

• Keep lesions clean with mild soap and lukewarm water; pat dry—avoid vigorous rubbing.
• Apply a thin layer of topical antibiotic ointment (e.g., bacitracin) if secondary infection is a concern.
• Wear loose, breathable clothing to reduce moisture buildup and friction.
• Protect ulcerated areas with sterile dressings changed daily.
• Maintain good nutrition (protein‑rich foods, vitamin C and zinc) to support skin healing.

Social considerations

• Inform school staff or community leaders about the diagnosis so that the child can receive support and avoid stigma.
• Participate in community mass‑treatment campaigns—treatment of close contacts reduces reinfection risk.
• Educate peers on avoiding direct contact with active lesions.

Physical activity

Gentle exercise is encouraged to maintain joint mobility, but avoid high‑impact sports that may traumatize bone lesions. A physiotherapist can design a tailored program.

Prevention

• Mass drug administration (MDA) – WHO recommends periodic community‑wide azithromycin distribution in hyper‑endemic areas to interrupt transmission.
• Early case detection – Training health workers and teachers to recognize primary yaws lesions leads to prompt treatment before progression.
• Improved hygiene – Regular hand/foot washing, use of clean water, and personal towels reduce skin‑to‑skin spread.
• Environmental measures – Providing footwear for children, constructing latrines, and avoiding communal sleeping mats diminish contact with infectious exudate.
• Vaccination research – No vaccine is currently licensed, but ongoing trials aim to develop a treponemal vaccine that could prevent yaws and related diseases.

Complications

If left untreated, secondary‑stage yaws can lead to:

• Severe disfigurement – Large ulcerating plaques may destroy tissue on the face, hands, or feet.
• Bone deformities – Chronic periostitis can cause bowing of long bones (sabre‑leg) or claw‑hand deformities.
• Secondary bacterial sepsis – Super‑infection of ulcerated lesions.
• Functional impairment – Joint pain and scarring can limit mobility, affecting school attendance and daily activities.
• Psychosocial impact – Stigma, low self‑esteem, and school dropout are documented in communities with high yaws prevalence.

When to Seek Emergency Care

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<sup>1</sup> World Health Organization. Yaws Fact Sheet. Updated 2022.

<sup>2</sup> WHO. Global Eradication of Yaws: Guidance for Programme Managers. 2020.

<sup>3</sup> Mitjà O, et al. "Azithromycin versus benzathine penicillin for the treatment of yaws." The New England Journal of Medicine. 2012;367:44‑50. DOI:10.1056/NEJMoa1200030.

All information presented here is for educational purposes and does not replace professional medical advice. Always consult a qualified health‑care provider for diagnosis and treatment.

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