An estimated 10% of people with yaws formerly were thought to develop tertiary disease symptoms, but more recently, tertiary yaws has been less frequently reported.Tertiary yaws can include gummatous nodules. It most commonly affects the skin. The skin of the palms and soles may thicken (hyperkeratosis). Nodules ulcerating near joints can cause tissue death. Periostitis can be much more severe. The shinbones may become bowed (saber shin) from chronic periostitis.Yaws may or may not have cardiovascular or neurological effects; definitive evidence is lacking. Rhinopharyngitis mutilans
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. This is now rare. Very rarely, yaws may cause bone spurs in the upper jaw near the nose (gondou); gondou was rare even when yaws was a common disease. Cause
The disease is transmitted by skin-to-skin contact with an infective lesion, with the bacterium entering through a pre-existing cut, bite, or scratch.Early (primary and secondary) yaws lesions have a higher bacterial load, thus are more infectious. Both papillomas and ulcers are infectious. Infectivity is thought to last 12–18 months after infection, longer if a relapse occurs. Early yaws lesions are often itchy, and more lesions may form along lines that are scratched.
Treatment
Treatment is normally by a single intramuscular injection of long-acting benzathine benzylpenicillin, or less commonly by a course of other antibiotics, such as azithromycin or tetracycline tablets. Penicillin has been the front-line treatment since at least the 1960s, but there is no solid evidence of the evolution of penicillin resistance in yaws.The historical strategy for the eradication of yaws (1952–1964) was:
Benzathine benzylpenicillin requires a cold chain and staff who can inject it, and there is a small risk of anaphylaxis. It was also not reliably available during the 2010s; there have been supply shortages.In the 2010s, a single oral dose of azithromycin was shown to be as effective as intramuscular penicillin. Unlike penicillin, there is strong evidence that yaws is evolving antibiotic resistance to azithromycin; there are two known mutations in the bacterium, each of which can cause resistance and make the treatment ineffective. This has threatened eradication efforts.Within 8–10 hours of penicillin treatment, bacteria can no longer be found in lesion biopsies. Primary and secondary lesions usually heal in 2–4 weeks; bone pain may improve within two days. If treated early enough, bone deformities may reverse and heal. Primary and secondary stage lesions may heal completely, but the destructive changes of tertiary yaws are largely irreversible.If lesions do not heal, or RPR test results do not improve, this may indicate treatment failure or re-infection; the treatment is typically repeated. WHO guidelines says that any presumed treatment failures at 4 weeks require macrolide resistance testing.