Yaws, also known as pian, parangi, paru, and frambesia tropica, is a chronic, relapsing skin infection characterized by bumps on the hands, feet, face, and genital area. Following the initial skin infection, the joints and bones may also become affected.
Yaws occurs mainly in warm, humid regions and mostly affects children under age 15. Risk factors include overcrowded living conditions and poor hygiene. Yaws is not typically seen in the United States; the incidence is highest in tropical areas of Africa, Asia, South and Central America, and the Pacific Islands. According to the World Health Organization, approximately 460,000 new cases of yaws are diagnosed annually.
Yaws is caused by the spirochete Treponema pertenue, which penetrates an area of broken skin, such as an insect bite, scrape, cut, or abrasion. The initial lesion, called the mother yaw, is a painless ulceration that takes 2 to 8 weeks to grow. It contains a large amount of spirochetes that can be transmitted from person to person via skin contact. In late yaws, the lesions are no longer contagious.
Complications of yaws include secondary bacterial infection and scarring. Similar to tertiary syphilis, bone, cartilage, skin, and soft tissue may be affected in untreated patients after 5 to 10 years. Resulting conditions may include gangosa (destructive ulcerations of the nasopharynx, palate, and nose); painful skeletal deformities, especially of the legs (termed saber shins); and other soft-tissue changes (gummas, inflammatory cell infiltration).
Yaws has four stages. In the primary stage, a large bump lesion develops up to 3 weeks after inoculation. Called the mother yaw, this lesion is also known as buba, buba madre, or primary frambesioma. It is slightly elevated with a crust that sheds, leaving an area that resembles the texture of a raspberry or strawberry. The lesion is painless, although lymph nodes in the area may be swollen. A light-colored scar remains when the lesion heals, usually in 2 to 9 months. Bone and joint pain and swelling may occur in early disease. Other symptoms include fatigue, general malaise, and anorexia.