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 cm (0.79 to 1.97 in) in diameter. The center may break open and form an ulcer. This initial skin lesion typically heals after 3–6 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 5 years or more, large areas of skin may die, leaving scars.Yaws is spread by direct contact with the fluid from a lesion of an infected person. The contact is usually of a nonsexual nature. The disease is most common among children, who spread it by playing together. Other related treponemal diseases are bejel (T. pallidum endemicum), pinta (T. carateum), and syphilis (T. p. 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  is the most accurate method of diagnosis.No vaccine has yet been found. Prevention is, in part, done 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 also decreases spread.
Serpiginous choroiditis, also known as geographic or helicoid choroidopathy, is an uncommon chronic progressive inflammatory disease affecting adult men and women equally in the second to seventh decades of life. Presentation
In this condition the posterior uveitis shows a geographic pattern. The inflammation begins in the juxtapapillary choroid and intermittently spreads centrifugally. The overlying retinal pigment epithelium and the outer retina are involved in the inflammatory process. A closely related condition is multifocal serpiginoid choroiditis. This is caused by tuberculosis.The distinction between these two conditions is important as the latter responds to anti tuberculosis treatment while the former does not. Diagnosis
Treatment
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