eMedicine Specialties > Infectious Diseases > Skin and Soft-Tissue Infections
Yaws
Updated: Nov 4, 2009
Introduction
Background
Yaws is a contagious, nonvenereal, treponemal infection in humans that mainly occurs in children younger than 15 years. Infection with Treponema pertenue, a subspecies of Treponema pallidum, causes the disease, which occurs primarily in warm, humid, tropical areas of Africa, Asia, South America, and Oceania among poor rural populations where conditions of overcrowding and poor sanitation prevail.
Pathophysiology
The major route of infection is through direct person-to-person contact. The treponemes associated with yaws are located primarily in the epidermis. The ulcerative skin lesions that develop early in the disease course are teeming with spirochetes, which can be transmitted via direct skin-to-skin contact and via breaks in the skin due to trauma, bites, or excoriations.
Yaws, like syphilis, has been classified into the following 4 stages:
- Primary stage: The initial yaws lesion develops at the inoculation site.
- Secondary stage: Widespread dissemination of treponemes results in multiple skin lesions similar to the primary yaws lesion.
- Latent stage: Symptoms are usually absent, but skin lesions can relapse.
- Tertiary stage: Bone, joint, and soft tissue deformities may occur.
Another classification distinguishes early yaws from late yaws. Early yaws includes primary and secondary stages and is characterized by the presence of contagious skin lesions. Late yaws includes the tertiary stage, when lesions are not contagious.
Frequency
United States
Yaws does not occur in the United States.
International
An estimated 50-100 million persons were infected with yaws before mass treatment campaigns in the 1950s. In the 1970s, yaws cases declined to fewer than 2 million. In the 1980s, fewer than 500 cases per year were reported in the Western Hemisphere. A resurgence of yaws has occurred in West and Central Africa, Southeast Asia, and the Pacific Islands, with recent outbreaks in Thailand, India, Indonesia, Papua New Guinea, and the Solomon Islands. Sporadic cases are reported in South America.
Mortality/Morbidity
- In most patients, yaws remains limited to the skin, but early bone and joint involvement can occur. Although yaws lesions disappear spontaneously, secondary bacterial infections and scarring are common complications.
- After 5-10 years, 10% of untreated patients develop destructive lesions that involve bone, cartilage, skin, and soft tissue, similar to those seen in tertiary syphilis. In contrast to venereal syphilis, cardiovascular and neurological abnormalities almost never occur in patients with yaws.
Sex
- Yaws has no sexual predilection.
Age
- Yaws predominantly affects children younger than 15 years. The peak incidence is in children aged 6-10 years.
Clinical
History
- Primary lesions, also called mother yaw, develop at the site of inoculation after an incubation period of 3 weeks (range, 9-90 d) (as seen in the image below).
Initial papilloma, also called mother yaw or primary frambesioma (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta. Geneva, Switzerland: World Health Organization; 1984.).
- The primary lesion often appears at a site of prior skin injury or an insect bite.
- During the incubation period, T pertenue invades the subcutaneous lymphatics and disseminates hematogenously.
- The initial yaws lesion is a papule that enlarges to become a papilloma or frambesioma.
- The yaws papilloma resolves spontaneously after 3-6 months.
- Secondary yaws lesions may occur near primary lesions or elsewhere on the body.
- Secondary yaws lesions may last for more than 6 months.
- Macules, papules, nodules, and hyperkeratotic lesions may appear (as seen in the image below).
Plantar papillomata with hyperkeratotic macular plantar early yaws (ie, crab yaws) (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta.Geneva, Switzerland: World Health Organization; 1984.).
- Hyperkeratosis, referred to as crab yaws, may appear on palms and soles.
- Lesions may ulcerate.
- Bone and joint involvement may occur in early disease and may cause pain and swelling.
- Climate influences the morphology and the number of lesions.
- In the dry season, lesions are fewer and macular in appearance. Papillomas are found in moist areas of axilla, skin folds, and mucosal surfaces.
- Secondary lesions heal spontaneously.
- During latent periods, skin lesions may relapse for as long as 5 years after infection.
- Most patients remain in a noninfectious latent stage for their lifetime.
- Late yaws develops in 10% of cases, usually 5-10 years after disease onset.
- Characteristic deformities, called saber shins (as seen in the image below), result from chronic untreated osteoperiostitis of the tibia.
Osteoperiostitis of the tibia and fibula in early yaws (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta. Geneva, Switzerland: World Health Organization; 1984.).
- Other lesions observed in patients with late yaws include monodactylitis, juxta-articular nodules, and gangosa (also called rhinopharyngitis mutilans), in which nasal cartilage is destroyed.
Physical
- Early yaws lesions
- Papilloma
- Serpiginous papilloma
- Ulceropapillomata
- Squamous macules (as seen in the image below)
Squamous macular palmar yaws (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta. Geneva, Switzerland: World Health Organization; 1984.).
- Maculopapules
- Nodules
- Plaques
- Hyperkeratosis of palms and soles
- Bone and joint lesions
- Generalized lymphadenopathy (may occur)
- Late yaws lesions
- Hyperkeratosis
- Nodular scars
- Gangosa
- Saber tibia
- Goundou
- Monodactylitis
- Juxta-articular nodules
Causes
- T pertenue is the causative agent.
- T pertenue cannot be distinguished from T pallidum or Treponema carateum with morphology or laboratory tests.
More on Yaws |
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| Follow-up: Yaws |
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| References |
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References
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Further Reading
Keywords
yaws, framboesia, mother yaw, primary frambesioma, frambesia tropica, parangi, paru, buba, pian, bouba, endemic treponema, endemic treponematoses, treponemal infection, saber shins, hemagglutination, TPHA, microhemagglutination
