yaws

Yaws
Classification and external resources
Nodules on the elbow resulting from a Treponema pertenue bacterial infection.
ICD-10	A66.
ICD-9	102

Yaws (also Pétasse tropica, thymosis, polypapilloma tropicum, pian or parangi, "Bouba," "Frambesia," and "Pian"^[1]) is a tropical infection of the skin, bones and joints caused by the spirochete bacterium Treponema pallidum pertenue. Other treponemal diseases are bejel (Treponema pallidum endemicum), pinta (Treponema pallidum carateum), and syphilis (Treponema pallidum pallidum).

History

Examination of ancient remains has led to the suggestion that yaws has affected hominids for the last 1.5 million years. The current name is believed to be of Carib origin, "yaya" meaning sore.

Epidemiology

Yaws is found in humid tropical regions in South America, Africa, Asia and Oceania. Mass treatment campaigns in the 1950s reduced the worldwide prevalence from 50-100 million to fewer than 2 million; however during the 1970s there were outbreaks in south-east Asia and there have been continued sporadic cases in South America. It is unclear how many people worldwide are infected at present.

Presentation

The disease is transmitted by skin-to-skin contact with an infective lesion, the bacterium entering through a pre-existing cut, bite or scratch. Within ninety days (but usually less than a month) of infection a painless but distinctive 'mother yaw' appears, which is a painless nodule which enlarges and becomes warty in appearance. Sometimes nearby 'daughter yaws' also appear simultaneously. This primary stage resolves completely within six months. The secondary stage occurs months to years later, and is characterised by widespread skin lesions of varying appearance, including 'crab yaws' on the palms and soles with desquamation. These secondary lesions frequently ulcerate (and are then highly infectious), but heal after six months or more. About ten percent of people then go on to develop tertiary disease within five to ten years (during which further secondary lesions may come and go), characterised by widespread bone, joint and soft tissue destruction, which may include extensive destruction of the bone and cartilage of the nose (rhinopharyngitis mutilans or 'gangosa').

Diagnosis

Dark field microscopy of samples taken from early lesions (particularly ulcerative lesions) may show the responsible organism. Blood tests such as VDRL, Rapid Plasma Reagin (RPR) and TPHA will also be positive, but there are no current blood tests which distinguish between the four treponematoses.

Treatment

Treatment is normally by a single dose of intramuscular penicillin, or by a course of penicillin, erythromycin or tetracycline tablets. Early lesions may heal completely, but the destructive changes of tertiary yaws are largely irreversible.

References

1. ^ James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0. 

• McNeill, William H. "Plagues and People." Bantam Doubleday Dell Publishing Group, Inc., New York, NY, 1976, ISBN 0-385-12122-9.