The primary lesion of yaws is a small, nonindurated papule at the site of inoculation that appears within 3 to 5 weeks after infection. The lesion usually ulcerates and exudes a serous fluid containing infective treponemes. The papilloma is painless unless it becomes secondarily infected with bacteria. Draining lymph nodes are usually enlarged but not painful. The initial lesion, which most commonly occurs on one of the legs, heals after many months.
Secondary lesions appear after dissemination.
They may develop before the initial lesion has healed and may occur anywhere on the skin or at mucocutaneous borders, but they occur especially in moist intertriginous areas of the skin. Painful hyperkeratotic lesions may appear on the palms and especially on the soles. Periostitis develops and may produce pain in the tibia and other long bones. Such involvement may resolve without deformity or may lead to the development of saber tibia and polydactyly. Secondary lesions usually heal in about 6 months, but relapses may occur later, when yaws usually becomes latent.