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AUTHOR AND EDITOR INFORMATION

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Author: Natalie C Klein, MD, PhD, Associate Professor, Department of Medicine, Division of Infectious Diseases, SUNY School of Medicine at Stony Brook; Associate Director, Winthrop-University Hospital

Natalie C Klein is a member of the following medical societies: American College of Physicians, American Medical Association, American Society for Microbiology, Infectious Diseases Society of America, and New York County Medical Society

Editors: Gary L Gorby, MD, Program Director of Adult Infectious Diseases Fellowship, Associate Professor, Department of Internal Medicine, Division of Infectious Disease, St Joseph Medical Center, Creighton University School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Richard B Brown, MD, FACP, Chief, Division of Infectious Diseases, Baystate Medical Center; Professor, Department of Internal Medicine, Tufts University School of Medicine; Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital; Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Author and Editor Disclosure

Synonyms and related keywords: yaws, framboesia, mother yaw, primary frambesioma, frambesia tropica, parangi, paru, buba, pian, bouba, endemic treponema, endemic treponematoses, treponemal infection, Treponema pertenue, T pertenue, Treponema pallidum, T pallidum, hyperkeratosis, crab yaws, saber shins, Treponema carateum, T carateum, venereal syphilis, Treponema pallidum hemagglutination, TPHA, microhemagglutination Treponema pallidum, MHA-TP, fluorescent treponema antibody absorption, FTA-ABS, gangosa


INTRODUCTION

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Background

Yaws is a contagious, nonvenereal, treponemal infection in humans that mainly occurs in children younger than 15 years. Infection with Treponema pertenue, a subspecies of Treponema pallidum, causes the disease, which occurs primarily in warm, humid, tropical areas of Africa, Asia, South America, and Oceania among poor rural populations where conditions of overcrowding and poor sanitation prevail.

Pathophysiology

The major route of infection is through direct person-to-person contact. The treponemes associated with yaws are located primarily in the epidermis. The ulcerative skin lesions that develop early in the disease course are teeming with spirochetes, which can be transmitted via direct skin-to-skin contact and via breaks in the skin due to trauma, bites, or excoriations.

Yaws, like syphilis, has been classified into the following 4 stages:

  1. Primary stage: The initial yaws lesion develops at the inoculation site.
  2. Secondary stage: Widespread dissemination of treponemes results in multiple skin lesions similar to the primary yaws lesion.
  3. Latent stage: Symptoms are usually absent, but skin lesions can relapse.
  4. Tertiary stage: Bone, joint, and soft tissue deformities may occur.

Another classification distinguishes early yaws from late yaws. Early yaws includes primary and secondary stages and is characterized by the presence of contagious skin lesions. Late yaws includes the tertiary stage, when lesions are not contagious.

Frequency

United States

Yaws does not occur in the United States.

International

An estimated 50-100 million persons were infected before mass treatment campaigns in the 1950s. In the 1970s, yaws cases declined to fewer than 2 million. In the 1980s, fewer than 500 cases per year were reported in the Western Hemisphere. A resurgence of yaws has occurred in West and Central Africa, Southeast Asia, and the Pacific Islands, with recent outbreaks in Thailand, India, Indonesia, Papua New Guinea, and the Solomon Islands. Sporadic cases are reported in South America.

Mortality/Morbidity

  • In most patients, yaws remains limited to the skin, but early bone and joint involvement can occur. Although yaws lesions disappear spontaneously, secondary bacterial infections and scarring are common complications.
  • After 5-10 years, 10% of untreated patients develop destructive lesions that involve bone, cartilage, skin, and soft tissue, similar to those seen in tertiary syphilis. In contrast to venereal syphilis, cardiovascular and neurological abnormalities almost never occur in patients with yaws.

Sex

  • No sex predilection exists.

Age

  • Yaws predominantly affects children younger than 15 years. The peak incidence is in children aged 6-10 years.


CLINICAL

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History

  • Primary lesions, also called mother yaw, develop at the site of inoculation after an incubation period of 3 weeks (range, 9-90 d) (see Image 1).
  • The primary lesion often appears at a site of prior skin injury or an insect bite.
  • During the incubation period, T pertenue invades the subcutaneous lymphatics and disseminates hematogenously.
  • The initial yaws lesion is a papule that enlarges to become a papilloma or frambesioma.
  • The yaws papilloma resolves spontaneously after 3-6 months.
  • Secondary yaws lesions may occur near primary lesions or elsewhere on the body.
  • Secondary yaws lesions may last for more than 6 months.
  • Macules, papules, nodules, and hyperkeratotic lesions may appear (see Image 2).
  • Hyperkeratosis, referred to as crab yaws, may appear on palms and soles.
  • Lesions may ulcerate.
  • Bone and joint involvement may occur in early disease and may cause pain and swelling.
  • Climate influences the morphology and the number of lesions.
  • In the dry season, lesions are fewer and macular in appearance. Papillomas are found in moist areas of axilla, skin folds, and mucosal surfaces.
  • Secondary lesions heal spontaneously.
  • During latent periods, skin lesions may relapse for as long as 5 years after infection.
  • Most patients remain in a noninfectious latent stage for their lifetime.
  • Late yaws develops in 10% of cases, usually 5-10 years after disease onset.
  • Characteristic deformities, called saber shins (see Image 3), result from chronic untreated osteoperiostitis of the tibia.
  • Other lesions observed in patients with late yaws include monodactylitis, juxta-articular nodules, and gangosa (also called rhinopharyngitis mutilans), in which nasal cartilage is destroyed.

Physical

  • Early yaws lesions
    • Papilloma
    • Serpiginous papilloma
    • Ulceropapillomata
    • Squamous macules (see Image 6)
    • Maculopapules
    • Nodules
    • Plaques
    • Hyperkeratosis of palms and soles
    • Bone and joint lesions
    • Generalized lymphadenopathy (may occur)
  • Late yaws lesions
    • Hyperkeratosis
    • Nodular scars
    • Gangosa
    • Saber tibia
    • Goundou
    • Monodactylitis
    • Juxta-articular nodules

Causes

  • T pertenue is the causative agent.
  • T pertenue cannot be distinguished from T pallidum or Treponema carateum with morphology or laboratory tests.


DIFFERENTIALS

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Impetigo
Leishmaniasis
Leprosy
Molluscum Contagiosum
Sarcoidosis
Sickle Cell Anemia
Tuberculosis
Tungiasis

Other Problems to be Considered

Scabies
Tinea versicolor
Lichen planus
Tropical ulcer
Plantar warts
Psoriasis
Venereal syphilis
Endemic syphilis
Osteomyelitis


WORKUP

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Lab Studies

  • Yaws is usually diagnosed based on clinical findings.
  • Serodiagnostic tests for venereal syphilis are used to diagnose yaws.
  • Nontreponemal test (eg, rapid plasma reagent [RPR], Venereal Disease Research Laboratory [VDRL] test) results are positive in all stages, except very early lesions.
  • Confirmatory treponemal tests (eg, Treponema pallidum hemagglutination [TPHA], microhemagglutination Treponema pallidum [MHA-TP], fluorescent treponema antibody absorption [FTA-ABS]) are not practical in remote areas.
  • Results of dark-field examination of early lesions are positive.
  • Biopsy of late lesions may be needed to show characteristic histopathology.

Histologic Findings

Typical histopathology of early yaws shows papillomatous epidermal hyperplasia, focal spongiosis, and intraepidermal microabscesses. Treponemes are found in the epidermidis (see Images 4-5).


TREATMENT

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Medical Care

  • Administer antibiotics.


MEDICATION

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The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Drug Category: Antibiotics

Benzathine penicillin is the DOC for treating yaws. In remote areas where benzathine penicillin is unavailable, oral penicillin V for 7-10 days can reduce the prevalence of yaws and is effective in treating individual children with active lesions.1

Drug NameBenzathine penicillin G (Bicillin)
DescriptionInterferes with cell wall synthesis during active multiplication, resulting in bactericidal activity against susceptible microorganisms.
Adult Dose2.4 million U IM once in 2 injection sites
Pediatric Dose50,000 U/kg IM once; not to exceed 2.4 million U
ContraindicationsDocumented hypersensitivity
InteractionsProbenecid can increase penicillin effectiveness by decreasing its clearance; coadministration with tetracyclines can decrease effectiveness
PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
PrecautionsCaution in impaired renal function

Drug NameTetracycline (Achromycin, Sumycin)
DescriptionAvoid benzathine penicillin in patients allergic to penicillin; tetracycline or erythromycin is alternate therapy.
Adult Dose500 mg PO qid for 15 d
Pediatric Dose<8 years: Not recommended
>8 years: 25-50 mg/kg/d (10-20 mg/lb) PO qid
ContraindicationsDocumented hypersensitivity; severe hepatic dysfunction
InteractionsBioavailability decreases with antacids containing aluminum, calcium, magnesium, iron, or bismuth subsalicylate; can decrease effects of oral contraceptives, causing breakthrough bleeding and increased risk of pregnancy; tetracyclines can increase hypoprothrombinemic effects of anticoagulants
PregnancyD - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
PrecautionsPhotosensitivity may occur with prolonged exposure to sunlight or tanning equipment; reduce dose in renal impairment; consider drug serum level determinations in prolonged therapy; tetracycline use during tooth development (last half of pregnancy through age 8 y) can cause permanent discoloration of teeth; Fanconilike syndrome may occur with outdated tetracyclines

Drug NameErythromycin (Erythrocin, E-Mycin, E.E.S.)
DescriptionInhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest. For treatment of staphylococcal and streptococcal infections. Indicated for the treatment of infections in children allergic to penicillin or in pregnant women.
Adult Dose250 mg erythromycin stearate/base (or 400 mg ethylsuccinate) PO q6h 1 h ac or 500 mg q12h
Alternately, use 333 mg PO q8h; increase up to 4 g/d depending on severity of infection
Pediatric Dose30-50 mg/kg/d (15-25 mg/lb/d) PO in divided doses; for severe infections, double dose
ContraindicationsDocumented hypersensitivity; hepatic impairment
InteractionsTheophylline, digoxin, carbamazepine, and cyclosporine toxicity may increase when administered concurrently; may potentiate anticoagulant effects of warfarin; when taken concurrently with lovastatin and simvastatin, risks of rhabdomyolysis significantly increase
PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
PrecautionsCaution in liver disease; estolate preparation may cause cholestatic jaundice; adverse GI effects are common (doses should be given after meals); discontinue use if nausea, vomiting, malaise, abdominal colic, and/or fever occur


FOLLOW-UP

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Further Outpatient Care

  • After a single penicillin injection, early lesions become noninfectious after 24 hours and heal within 1-2 weeks.

Prognosis

  • The prognosis for early yaws is excellent.
  • Tissue damage occurring in late yaws is irreversible.


MISCELLANEOUS

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Medical/Legal Pitfalls

  • Failure to diagnose


MULTIMEDIA

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Media file 1:  Initial papilloma, also called mother yaw or primary frambesioma (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta. Geneva, Switzerland: World Health Organization; 1984.).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo

Media file 2:  Plantar papillomata with hyperkeratotic macular plantar early yaws (ie, crab yaws) (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta.Geneva, Switzerland: World Health Organization; 1984.).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo

Media file 3:  Osteoperiostitis of the tibia and fibula in early yaws (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta. Geneva, Switzerland: World Health Organization; 1984.).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo

Media file 4:  Early yaws papillomata (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta. Geneva, Switzerland: World Health Organization; 1984.).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo

Media file 5:  Early ulceropapillomatous yaws on the leg (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta. Geneva, Switzerland: World Health Organization; 1984.).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo

Media file 6:  Squamous macular palmar yaws (from Perine PL, Hopkins DR, Niemel PLA, et al. Handbook of Endemic Treponematoses: Yaws, Endemic Syphilis, and Pinta. Geneva, Switzerland: World Health Organization; 1984.).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo


REFERENCES

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Yaws excerpt

Article Last Updated: Nov 16, 2007