MedTerms Medical Dictionary

Yaws: A common chronic infectious disease that occurs mainly in the warm humid regions of the tropics with characteristic bumps on the skin of the face, hands, feet and genital area. Almost all cases of yaws are in children under 15 years of age.

The organism that causes yaws is a spirochete. It is spiral shaped, as are all spirochetes, and is termed Treponema pertenue. (A different type of spirochete, Treponema pallidum, is the organism responsible for syphilis).

Yaws begins when the spirochete enters the skin at a spot where it was scraped, cut or otherwise compromised. At that site a painless bump arises and grows. It is the mother yaw. The glands in that area are often swollen (regional lymphadenopathy). The mother yaw heals, leaving a light-colored scar.

The mother yaw is followed by recurring ("secondary") crops of bumps and more swollen glands. These bumps may be painless like the mother yaw or they may be filled with pus, burst and ulcerate.

In its late ("tertiary") stage, yaws can destroy areas of the skin and bones and joints and deform them. The palms and soles tend to become thickened and painful ("dry crab yaws").

The diagnosis of yaws comes to the fore in any child who has the characteristic clinical features and lives in an area where the disease is common. With increasing travel, a child once in the tropics may carry the disease to a more temperate clime. Confirmation of the diagnosis is by blood tests and by special (dark- field) examination under the microscope (to see the spirochete).

Treatment of yaws is simple and highly effective. A single shot of penicillin cures the disease. Anyone allergic to penicillin can be treated with another antibiotic, usually erythromycin or tetracycline.

Yaws is a major public health problem in the tropics. Tropical regions in Central and South America, Africa, Asia, and Polynesia are at risk for yaws. A high percentage of children can be infected. Transmission of the disease is facilitated by overcrowding and poor hygiene, in the favellas of the cities of northeastern Brazil.

Yaws can be completely eradicated from an area by giving penicillin or another appropriate antibiotic to everyone in the population. This may, unfortunately, cost more than a poor country can afford.

The term "yaws" is of Caribbean origin. Because the bumps of yaws look like little berries, the disease is also called frambesia (or frambesia tropica) from the French "framboise" meaning "raspberry." Other names include granuloma tropicum polypapilloma tropicum, and thymiosis.

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