Yaws Skin Lesions

What is Yaws skin lesions?

Yaws is a chronic, contagious skin disease caused by the bacterium Treponema pallidum pertene. It primarily affects children living in warm, humid, tropical regions with limited access to health care. The hallmark of yaws is a series of distinctive skin lesions that progress through several stages—primary (a painless “mother” ulcer), secondary (multiple papules, nodules, or ulcerative lesions), and tertiary (gummatous tissue destruction). These lesions are the most visible sign of infection and can lead to scarring, disfigurement, and, rarely, bone involvement if left untreated.

While yaws was once nearly eradicated, recent WHO surveillance shows a resurgence in parts of West Africa, Southeast Asia, and the Pacific Islands. Understanding the appearance, causes, and management of the skin manifestations is essential for early detection and community control.

Common Causes

Although “yaws skin lesions” refer specifically to lesions caused by T. pallidum pertene, several other diseases can produce similar‑appearing rashes or ulcers. Recognizing these different entities helps clinicians avoid misdiagnosis.

• Yaws (Treponema pallidum pertene) – the primary cause.
• Bejel (Endemic syphilis, Treponema pallidum endemicum) – another non‑venereal treponemal disease, often with oral rather than skin lesions.
• Venereal syphilis (Treponema pallidum pallidum) – can mimic yaws lesions, especially in adults.
• Haemophilus ducreyi infection – causes chancroid‑like ulcers that may be confused with secondary yaws lesions.
• Leprosy (Mycobacterium leprae) – hypo‑pigmented patches and nodules that can resemble early yaws.
• Cutaneous leishmaniasis – ulcerative lesions in tropical areas, often with a raised border.
• Buruli ulcer (Mycobacterium ulcerans) – necrotic ulcers that may be mistaken for tertiary yaws lesions.
• Chronic fungal infections (e.g., chromoblastomycosis) – verrucous plaques that can be confused with yaws papules.
• Dermatophytosis (tinea corporis) – ring‑shaped lesions that may coexist with yaws.
• Autoimmune disorders (e.g., cutaneous lupus) – can produce erythematous plaques mimicking secondary yaws.

Associated Symptoms

Yaws skin lesions rarely appear in isolation. The disease often presents with a constellation of systemic and local signs that evolve over time.

• Fever and malaise – common during the secondary stage.
• Joint pain (arthralgia) – especially in the knees and ankles.
• Bone pain or swelling – can occur in tertiary yaws (osteitis/osteomyelitis).
• Lymphadenopathy – enlarged, often painless lymph nodes near the lesion.
• Hyperpigmented or hypopigmented patches – may persist after ulcer healing.
• Scarring and disfigurement – especially after repeated secondary lesions.
• Secondary bacterial infection – redness, pus, or increased pain at the lesion site.

When to See a Doctor

Prompt medical evaluation is crucial to halt disease spread and prevent complications.

• Any painless ulcer or raised skin nodule that persists > 2 weeks, especially in a child living in or returning from a tropical region.
• Development of multiple lesions after an initial “mother ulcer.”
• Fever, joint pain, or swollen lymph nodes accompanying skin changes.
• Signs of secondary bacterial infection (redness spreading, warmth, pus, increasing pain).
• Any concern for bone pain, especially if it limits walking or causes swelling.
• Pregnancy or immune‑compromised states (e.g., HIV) where infection may behave atypically.

Diagnosis

Accurate diagnosis integrates clinical assessment, laboratory testing, and, when needed, imaging.

Clinical Evaluation

• Detailed travel and exposure history (living in or visiting endemic areas).
• Physical examination of lesions: primary lesions are typically solitary, well‑circumscribed ulcers with a raised, thickened border; secondary lesions are multiple, may be papillomatous, ulcerative, or crusted.
• Assessment for systemic signs (fever, joint involvement, lymphadenopathy).

Laboratory Tests

• Serologic tests: Non‑treponemal tests (RPR, VDRL) and treponemal tests (TPPA, FTA‑ABS) are used. In yaws, non‑treponemal titres are usually lower than in venereal syphilis, but a positive treponemal test confirms infection.
• Dark‑field microscopy: Direct visualization of spirochetes from lesion exudate; requires expertise and is less commonly available.
• Polymerase chain reaction (PCR): Detects treponemal DNA and can differentiate yaws from syphilis, though it is mostly limited to research settings.
• Rapid diagnostic tests (RDTs):** Point‑of‑care treponemal assays are increasingly used in field surveys.