Rhinopharyngitis mutilans, also known as gangosa, is a destructive ulcerative condition that usually originates about the soft palate and spreads into the hard palate, nasopharynx, and nose, resulting in mutilating cicatrices, and outward to the face, eroding intervening bone, cartilage, and soft tissues. It occurs in late stages of yaws, usually 5 to 10 years after first symptoms of infection.

Within 90 days (but usually less than a month) of infection a painless but distinctive "mother yaw" nodule appears, which enlarges and becomes warty in appearance. Nearby "daughter yaws" may also appear simultaneously.

This primary stage resolves completely within six months. The secondary stage occurs months to years later, with typically widespread skin lesions that vary in appearance, including "crab yaws" on the palms of the hands and soles of the feet with desquamation. These secondary lesions frequently ulcerate and are then highly infectious, but heal after six months or more. About 10% of people then go on to develop tertiary disease within five to ten years (during which further secondary lesions may come and go), with widespread bone, joint and soft tissue destruction, which may include extensive destruction of the bone and cartilage of the nose (Rhinopharyngitis mutilans or "gangosa").

Yaws is a tropical infection of the skin, bones and joints caused by the spirochete bacterium "Treponema pallidum pertenue". The disease begins with a round, hard swelling of the skin, 2 to 5 centimeters in diameter. The center may break open and form an ulcer. This initial skin lesion typically heals after three to six months. After weeks to years, joints and bones may become painful, fatigue may develop, and new skin lesions may appear. The skin of the palms of the hands and the soles of the feet may become thick and break open. The bones (especially those of the nose) may become misshapen. After five years or more large areas of skin may die, leaving a scar.

Yaws is spread by direct contact with the fluid from a lesion of an infected person. The contact is usually of a non-sexual nature. The disease is most common among children, who spread it by playing together. Other related treponemal diseases are bejel ("Treponema pallidum endemicum"), pinta ("Treponema pallidum carateum"), and syphilis ("Treponema pallidum pallidum"). Yaws is often diagnosed by the appearance of the lesions. Blood antibody tests may be useful but cannot separate previous from current infections. Polymerase chain reaction (PCR) is the most accurate method of diagnosis.

Prevention is, in part, by curing those who have the disease thereby decreasing the risk of transmission. Where the disease is common, treating the entire community is effective. Improving cleanliness and sanitation will also decrease spread. Treatment is typically with antibiotics including: azithromycin by mouth or benzathine penicillin by injection. Without treatment, physical deformities occur in 10% of cases.

Yaws is common in at least 14 tropical countries as of 2012. The disease only infects humans. In the 1950s and 1960s the World Health Organization (WHO) nearly eradicated yaws. Since then the number of cases has increased and there are renewed efforts to globally eradicate the disease by 2020. The last estimate of the number of people infected was more than 500,000 in 1995. Although one of the first descriptions of the disease was made in 1679 by Willem Piso, archaeological evidence suggests that yaws may have been present among humans as far back as 1.6 million years ago.