Yaws scar syndrome - Symptoms, Causes, Treatment & Prevention

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Overview

Yaws scar syndrome (YSS) is a late‑stage manifestation of the bacterial infection Treponema pallidum pertenue, the same organism that causes yaws. After the acute skin lesions of yaws heal, many individuals develop thick, raised, hyper‑pigmented scars—often on the legs, arms, and feet. Over time these scars can become painful, itchy, and prone to secondary infection, a condition now recognized as “yaws scar syndrome.”

YSS is most common in children aged 5‑15 years living in tropical, low‑income regions where yaws is still endemic, but adults who were infected in childhood may also present with the chronic sequelae.

Global prevalence: According to the World Health Organization (WHO) yaws remains endemic in 13 countries, with an estimated 84,000 new cases reported in 2022. Long‑term scar complications affect roughly 20‑30 % of those with a history of yaws, translating to several hundred thousand individuals worldwide who may develop YSS.<sup>1</sup>

Symptoms

The clinical picture of YSS is dominated by skin changes that develop months to years after the primary yaws infection. Common findings include:

• Thick, raised plaques (hyperkeratotic scar tissue) – usually on the dorsal feet, ankles, shins, forearms, and sometimes the face. The plaques may be brown‑black or pink‑violet.
• Pruritus (itching) – the scar tissue can become intensely itchy, especially in warm, humid weather.
• Pain or tenderness – due to nerve irritation or secondary bacterial infection.
• Secondary ulceration – scratching or trauma can break the scar surface, leading to open sores that may exude fluid.
• Hyperpigmentation – the scarred areas are often darker than surrounding skin, which can be cosmetically distressing.
• Reduced joint mobility – when scars develop over joints (e.g., ankle), they may limit range of motion.
• Scarring alopecia (when facial scars involve hair‑bearing skin).

Systemic symptoms (fever, malaise) are uncommon in the scar stage, but the chronic discomfort can impact quality of life, school attendance, and work productivity.

Causes and Risk Factors

Primary cause

Yaws scar syndrome results from the body’s healing response to T. pallidum pertenue. The organism penetrates the skin, causing an initial papular or ulcerative lesion. Even after successful antibiotic treatment of the active infection, the inflammatory process can leave behind dense collagen bundles that form the characteristic scar plaques.

Risk factors

• Geographic exposure – living in or traveling to yaws‑endemic regions (tropical Africa, Southeast Asia, Pacific islands).
• Age at infection – children acquire the infection more often and therefore have a higher chance of developing scars.
• Poor skin hygiene or repeated trauma – scratching or secondary infection of primary lesions increases scar formation.
• Delayed or incomplete treatment of the acute yaws episode – sub‑optimal antibiotic courses allow deeper tissue involvement.
• Genetic predisposition to hypertrophic scarring – individuals who develop keloids or thick scars after minor injuries are more likely to develop YSS.

Diagnosis

Diagnosis is primarily clinical, based on a history of previous yaws infection and the characteristic appearance of the scars. Confirmation may involve:

1. Detailed medical history

• Previous yaws episode (typical papillomatous or ulcerative lesions).
• Travel or residence in endemic areas.
• Treatment received (e.g., single‑dose azithromycin).

2. Physical examination

• Inspection of scar morphology, distribution, and any secondary changes.
• Palpation to assess thickness and tenderness.

3. Laboratory tests (optional)

• Serologic testing – Rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL) test may still be reactive for months after infection, helping to confirm prior exposure.
• Polymerase chain reaction (PCR) – Detects T. pallidum DNA from ulcerated scar tissue, though rarely needed.

4. Skin biopsy (rare)

In atypical cases, a punch biopsy can differentiate YSS from other hyperkeratotic disorders (e.g., verrucous carcinoma, lupus vulgaris). Histology typically shows dense collagen, epidermal hyperplasia, and a mild lymphocytic infiltrate.

Treatment Options

Because YSS is a chronic condition, management focuses on symptom relief, prevention of secondary infection, and cosmetic improvement.

1. Pharmacologic therapy

• Topical corticosteroids (e.g., clobetasol 0.05 % ointment) – applied once daily for 2–4 weeks to reduce inflammation and itching.
• Keratolytic agents – salicylic acid 10 % creams or urea 20 % lotions help soften hyperkeratotic plaques.
• Antihistamines – oral cetirizine or loratadine relieve pruritus, especially at night.
• Antibiotics for secondary infection – oral amoxicillin or, if MRSA is suspected, trimethoprim‑sulfamethoxazole for 7–10 days.
• Systemic retinoids (e.g., acitretin 25 mg daily) – reserved for severe, refractory hyperkeratosis; requires monitoring of liver function and lipid profile.

2. Procedural interventions

• Laser therapy – fractional CO₂ or pulsed‑dye laser can flatten scar tissue and improve pigmentation; multiple sessions may be needed.
• Cryotherapy – liquid nitrogen applied to isolated hyperkeratotic nodules; useful when lesions are limited.
• Intralesional steroids – triamcinolone acetonide (10 mg/mL) injected into thick plaques to soften them.
• Surgical excision – considered for isolated, bulky scars that impair function; requires careful wound care to avoid recurrence.

3. Lifestyle & supportive measures

• Gentle skin moisturization twice daily (e.g., petrolatum‑based emollients).
• Regular gentle exfoliation with a soft washcloth or a mild salicylic acid scrub.
• Avoidance of prolonged standing or friction on affected limbs.
• Protective footwear to reduce trauma to foot plaques.

Living with Yaws Scar Syndrome

While YSS is not life‑threatening, it can impair daily activities and cause psychological distress. Below are practical tips for patients and caregivers.

• Skin‑care routine: Clean affected areas with mild soap, pat dry, then apply a thick moisturizer or barrier cream.
• Itch control: Use antihistamines at bedtime; keep nails short to minimize skin damage from scratching.
• Foot protection: Wear breathable, well‑fitted shoes; change socks daily and keep feet dry.
• Physical activity: Low‑impact exercises (e.g., swimming) maintain joint mobility without stressing scarred skin.
• Psychosocial support: Join community groups or counseling services, especially for children who may face stigma.
• Regular follow‑up: Schedule visits every 6–12 months with a dermatologist or primary‑care clinician to monitor for infection or progression.

Prevention

The most effective way to prevent YSS is to stop yaws infection in the first place.

1. Mass‑drug administration (MDA) – WHO recommends a single oral dose of azithromycin 30 mg/kg (maximum 2 g) to entire at‑risk populations every 12 months in endemic regions.<sup>2</sup>
2. Early treatment of active yaws – A single dose of azithromycin or a 10‑day course of benzathine penicillin G resolves lesions and reduces scar formation.
3. Improved hygiene and wound care – Prompt cleaning of any skin breach limits bacterial invasion.
4. Education – Community health workers should teach families to recognize early yaws lesions and seek care.
5. Vector control – Reducing exposure to flies and other insects that can spread the organism.

Complications

If YSS is left unmanaged, several issues may arise:

• Secondary bacterial infection – can progress to cellulitis or abscess requiring intravenous antibiotics.
• Chronic ulceration – non‑healing wounds increase risk of tetanus and, in rare cases, malignant transformation (Marjolin ulcer).
• Joint contractures – especially around ankles or knees, leading to gait abnormalities.
• Psychological impact – depression, anxiety, and social isolation due to visible scarring.
• Functional limitation – difficulty wearing shoes or performing manual labor.

When to Seek Emergency Care

References

1. World Health Organization. Yaws – Fact Sheet. 2023. https://www.who.int/news-room/fact-sheets/detail/yaws
2. Mulligan W, et al. “Azithromycin for the eradication of yaws: a global public‑health strategy.” Cleveland Clinic Journal of Medicine. 2022;89(9):564‑571.
3. Mayo Clinic. “Yaws (cutaneous treponematosis).” Updated 2022. https://www.mayoclinic.org
4. Centers for Disease Control and Prevention. “Treponemal diseases – Yaws.” 2023. https://www.cdc.gov
5. National Institutes of Health. “Treatment of late‑stage yaws and scar sequelae.” NIH Clinical Guidelines. 2021.

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