page_title: Yaws
section_title: Diagnosis
hierarchical_section_title: Yaws / Diagnosis
caption_attribution_description: English: Biopsy of a yaws lesion of a 10-year-old boy from Cotabato Province. Low-power view; for high-power view, see File:Moderately dense infiltrate of plasma cells and lymphocytes in the papillary dermis. See File:Large, “moist cauliflower” papillomas on left axilla.jpg for macroscopic view of the yaws lesion from which the biopsy was taken. From original CC-BY report: "Histopathologic findings of yaws papilloma A skin punch biopsy of the papilloma on the left axilla of the index case (Case 1) was performed by the principal investigator in the Rural Health Center 2 weeks post-treatment. The specimen was processed in the Philippine General Hospital and read by a dermatopathologist of the Division of Dermatology. The biopsy showed psoriasiform epidermal hyperplasia and band-like lymphocytic infiltrates in the papillary dermis, with thickening of the basement membrane. There were moderately dense infiltrates of plasma cells and lymphocytes in the papillary dermis. The histopathologic diagnosis was lichenoid psoriasiform dermatitis with plasma cells. These findings were consistent with yaws "
context_page_description: 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 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, pinta, and syphilis. 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.
  There is no vaccine.
context_section_description: Most often the diagnosis is made clinically. Dark field microscopy of samples taken from early lesions (particularly ulcerative lesions) may show the responsible bacteria; the spirochaetes are only 0.3 µm wide by 6–20 µm long, so light-field microscopy does not suffice.
  A microscopic examination of a biopsy of a yaw may show skin with clear epidermal hyperplasia (a type of skin thickening) and papillomatosis (a type of surface irregularity), often with focal spongiosis (an accumulation of fluid in specific part of the epidermis). Immune-system cells, neutrophils and plasma cells, accumulate in the skin, in densities that may cause microabscesses.
  Warthin-Starry or Levaditi silver stains selectively stain T. pallidum, and direct and indirect immunofluorescence and immunoperoxidase tests can detect polyclonal antibodies to T. pallidums. Histology often shows some spatial features which distinguish yaws from syphilis (syphilis is more likely to be found in the dermis, not the epidermis, and shows more endothelial cell proliferation and vascular obliteration).
  Blood-serum (serological) tests are increasingly done at the point of care. They include a growing range of treponemal and non-treponemal assays. Treponemal tests are more specific, and are positive for any one who has ever been infected with yaws; they include the Treponema pallidum particle agglutination assay. Non-treponemal assays can be used to indicate the progress of an infection and a cure, and positive results weaken and may become negative after recovery, especially after a case treated early. They include the venereal disease research laboratory (VDRL; requires microscopy) and rapid plasma reagin (RPR; naked-eye result) tests, both of which flocculate patient-derived antibodies with antigens.
  Serological tests cannot distinguish yaws from the closely related syphilis; no test distinguishing yaws from syphilis is widely available. The two genomes differ by about 0.2%. PCR and DNA sequencing can distinguish the two. There are also no common blood tests which distinguish among the four treponematoses: syphilis (Treponema pallidum pallidum), yaws (Treponema pallidum pertenue), bejel (Treponema pallidum endemicum), and pinta (Treponema carateum).
  Haemophilus ducreyi infections can cause skin conditions that mimic primary yaws. People infected with Haemophilus ducreyi lesions may or may not also have latent yaws, and thus may or may not test positive on serological tests. This was discovered in the mid 2010s. It seems that a recently diverged strain of Haemophilus ducreyi has evolved from being a sexually transmitted infection to being a skin ulcer pathogen that looks like yaws.
  Yaws has been reported in non-endemic countries.
caption: Lesion biopsy under a microscope; clear epidermal hyperplasia.
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