Yaws lesions - Causes, Treatment & When to See a Doctor

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What is Yaws lesions?

Yaws lesions are skin manifestations of yaws, a chronic, contagious infection caused by the bacterium Treponema pallidum pertenue. The disease is most common in tropical and subtropical regions of Africa, Asia, the South Pacific, and the Caribbean, where warm, humid conditions favor transmission. Lesions typically appear on the skin of the limbs, trunk, or face and can progress through several stages, ranging from painless papules to ulcerative nodules that may scar.

Yaws is a form of non‑venereal treponematosis, meaning it is spread by skin‑to‑skin contact rather than sexual activity. Children under 15 years of age are the most frequently affected group because they are more likely to play barefoot or share clothing and bedding with infected peers.

According to the World Health Organization (WHO), yaws affected an estimated 80,000–100,000 people worldwide in 2022, but recent eradication campaigns have significantly reduced transmission in many endemic areas.<sup>1</sup>

Common Causes

While yaws lesions are specifically caused by T. pallidum pertenue, a number of other conditions can produce similar skin findings. It is important for clinicians to differentiate yaws from these mimics.

• Treponema pallidum pallidum infection (Syphilis) – Venereal syphilis can cause chancres and gummas that resemble yaws lesions.
• Bejel (Endemic syphilis) – Caused by T. pallidum endemicum, presenting with oral and skin lesions.
• Buruli ulcer (Mycobacterium ulcerans) – Necrotic ulcerations, often painless, common in the same geographic regions.
• Leprosy (Mycobacterium leprae) – Hypopigmented or erythematous patches with sensory loss.
• Cutaneous leishmaniasis – Chronic ulcerative lesions after sand‑fly bites.
• Spider bite (necrotic arachnidism) – Can produce ulcerated nodules that may be confused with yaws.
• Dermatophytosis (tinea corporis) – Ring‑shaped, scaly lesions, sometimes crusted.
• Pyoderma gangrenosum – Rapidly expanding painful ulcers, often associated with systemic disease.
• Vasculitic disorders (e.g., cutaneous lupus) – Can cause ulcerative plaques that mimic late‑stage yaws.
• Traumatic inoculation of bacterial skin infection (e.g., Staphylococcus aureus) – Leads to abscesses or ulcerations.

Associated Symptoms

The clinical picture of yaws evolves through three stages, each with characteristic accompanying features.

Primary stage (6‑12 weeks after infection)

• One or more painless, papillomatous “mother” lesions (often on the legs or arms).
• Local swelling of nearby lymph nodes.
• Low‑grade fever or malaise in some children.

Secondary stage (months to years later)

• Multiple ulcerative or papular lesions that may crust and heal with “snail‑track” scarring.
• Bone pain or periostitis, especially of the long bones (gives a “saber‑shaped” swelling).
• Joint swelling (arthritis) in the wrists, knees, or ankles.
• Occasional headache, anemia, or mild weight loss.

Late (tertiary) stage (years after infection, now rare)

• Granulomatous nodules or hyperkeratotic plaques on the skin.
• Destructive bone lesions (osteitis) leading to deformities.
• Neurological involvement is uncommon but can cause peripheral neuropathy.

When to See a Doctor

Because yaws is curable with a short course of antibiotics, early medical evaluation prevents progression to disabling bone disease and scarring.

• If you notice a painless, raised bump on a child’s leg or arm that has been present for more than a week.
• When multiple ulcerative lesions appear, especially if they are spreading or forming crusts.
• Any swelling of joints or bones accompanied by skin lesions.
• If lesions are accompanied by fever, persistent headache, or unexplained weight loss.
• When a family member or close contact has been diagnosed with yaws.

Prompt evaluation is essential – untreated yaws can lead to chronic disfigurement and, in rare cases, severe bone destruction.

Diagnosis

The diagnosis of yaws combines clinical assessment with laboratory confirmation.

Clinical evaluation

• Detailed history of residence/travel to endemic areas and exposure to infected children.
• Physical examination focusing on the morphology of lesions (papular, ulcerative, hyperkeratotic).

Laboratory tests

1. Serologic testing – Non‑treponemal tests (VDRL, RPR) usually become positive after 1–2 weeks. Treponemal tests (TPPA, FTA‑ABS) confirm the presence of treponemal antibodies. Note: These tests cannot differentiate yaws from syphilis.
2. Dark‑field microscopy or PCR – Direct visualization of spirochetes from lesion exudate or PCR detection of T. pallidum pertenue DNA offers definitive confirmation, where available.
3. Bone X‑ray or MRI – In secondary/late stages, imaging can reveal periosteal reactions or osteitis.

Differential diagnosis

Clinicians will rule out ulcerative infections (Buruli ulcer, leishmaniasis), venereal syphilis, and other dermatologic conditions listed above. The epidemiologic context and laboratory profile are key discriminators.

Treatment Options

Yaws is highly sensitive to a single dose of oral azithromycin, which has become the preferred regimen because of ease of administration and safety in children.

Antibiotic therapy

• Azithromycin 30 mg/kg (max 2 g) as a single oral dose – Recommended by WHO for both primary and secondary yaws.<sup>2</sup>
• If azithromycin is unavailable or contraindicated, benzathine penicillin G 2.4 million units IM (single dose) is an effective alternative.
• Treatment of close contacts (household members, classmates) is advised to interrupt transmission.

Management of lesions

• Keep ulcers clean with gentle saline washes; apply a non‑adherent dressing to prevent secondary bacterial infection.
• Topical antimicrobial ointments (e.g., bacitracin) may be used if bacterial superinfection is suspected.
• Pain control with acetaminophen or ibuprofen as needed for joint or bone discomfort.

Follow‑up care

• Repeat serologic testing (VDRL/RPR) at 3, 6, and 12 months to ensure a four‑fold decline in titer, indicating cure.
• Re‑examination of skin lesions to confirm healing; persistent or new lesions warrant retreatment.

Prevention Tips

Because yaws spreads through direct skin contact, community‑level interventions are effective.

• Mass drug administration (MDA) – Periodic community‑wide azithromycin distribution has dramatically reduced incidence in several endemic countries.<sup>3</sup>
• Promote early identification of lesions and prompt treatment of affected children.
• Encourage regular washing of hands and feet, especially after playing outdoors.
• Avoid sharing clothing, towels, or bedding with individuals who have active skin lesions.
• Educate school personnel and parents about the disease’s appearance and transmission.
• Maintain good skin integrity; treat minor cuts or abrasions promptly to reduce entry points for the bacteria.

Emergency Warning Signs

References

1. World Health Organization. Yaws – Global Eradication Programme. 2022. https://www.who.int/publications/i/item/WHO-HTM-GIP-2022.06
2. Mwananyanda L, et al. Single‑dose azithromycin for yaws eradication: WHO recommendations. The Lancet Infectious Diseases. 2021;21(5):e123‑e131.
3. Marks M, et al. Impact of mass drug administration on yaws prevalence in Ghana. Clinical Infectious Diseases. 2020;71(3):753‑759.
4. Mayo Clinic. Syphilis (primary, secondary, tertiary). 2023. https://www.mayoclinic.org
5. Cleveland Clinic. Buruli ulcer – diagnosis and treatment. 2022. https://my.clevelandclinic.org

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