Yaws and pinta are caused respectively by the spirochaetes Treponema pertenue and T. carateum (invalid). Although closely related to T. pallidum which causes syphilis, neither organism is transmitted by sexual contact. Intensive campaigns organized by WHO and UNICEF virtually eradicated these diseases in the 1950s, but yaws is now widely endemic in tropical areas, while pinta is confined to the American tropics. Both diseases are spread among children by direct contact. Exudate from infectious primary lesions gains access to deeper layers of the skin through minor skin abrasions or cheilitic lesions associated with vitamin B deficiency.

Yaws is heralded, after an incubation period of 3-5 weeks, by a small papule, usually on the lower leg or foot. Occasionally, however, night pain in the legs resulting from periosteal inflammation of the long bones is the first indication of the disease. The primary skin lesion rapidly enlarges into a fleshy, ulcerated papilloma, which exudes a serous fluid containing many treponemes. Secondary cutaneous papillomatous or papulosquamous lesions may appear anywhere, but are typically found in moist areas and at mucocutaneous junctions. Pain and swelling of the small joints of the hand is also typical of the early disseminated phase of the disease. The initial acute inflammatory lesions usually resolve completely within a few months, but subsequent relapses may leave extensive cutaneous scars. Prolonged periostitis results in “sabre tibia” and other characteristic bone deformities. For several years, however, episodes of hyperkeratosis with fissuring and ulceration of the soles of the feet often provide the only indication of continued activity of the disease. Later, gummatous lesions of the skin similar to those of syphilis and destructive lesions of the bone may occur. Gummatous cranial periostitis and destruction of the palatal and nasal cartilage are also typical and serious complications of the late stages of the disease.

Pinta is a comparatively benign condition in which only the skin is involved. The primary lesion is usually psoriasiform in appearance and often attains a diameter of several centimetres. This, and other lesions which may develop subsequently, gradually lose their initial violet colour to leave depigmented and atrophic scars.

Treatment

A single dose of 2.4 million IU of benzathine benzylpenicillin (1.2 million IU for children) should be administered in two intramuscular injections to avert all risk of relapse. Patients who are sensitive to penicillin should receive tetracycline provided they are over 8 years of age, while younger patients should be given erythromycin.