AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Background

Yaws is the most prevalent infectious, nonvenereal, treponemal disease and is caused by Treponema pallidum subsp pertenue. The disease is transmitted by direct skin contact and usually affects children, with a peak incidence in those aged 6-10 years. Similar to syphilis, yaws can persist for years as a chronic, relapsing disease.

Yaws continues to be endemic along the tropical belt in areas characterized by hot temperatures, high humidity, and heavy rainfall. These conditions coupled with the persistence of poverty, poor sanitation, overcrowding, and lack of public health surveillance allow for disease perpetuation.

Pathophysiology

Cutaneous lesions characterize the primary and secondary stages. The tertiary stage may include involvement of skin, bones, and joints.

Frequency

International

In the early 1950s, the estimated number of active cases in areas of Africa, Asia, South America, Central America, and the Pacific Islands was 25-150 million. After the World Health Organization (WHO) supported mass treatment campaigns from 1954-1963, researchers observed a dramatic fall in the prevalence. Since then, however, cases of yaws rebounded because of the lack of public health surveillance and inadequate treatment facilities. Currently, researchers estimate that 100 million children are at risk of acquiring yaws.

Mortality/Morbidity

Unless treated, yaws can become a chronic, relapsing disease with skin, bone, and joint involvement. In 10% of cases, patients enter a late stage (tertiary stage) characterized by destructive cutaneous lesions and severely deforming bone and joint lesions. Neurologic and ophthalmologic involvement may also occur.

Sex

No sexual predilection exists.

Age

Children serve as the primary reservoir for yaws. It is most common in children younger than 15 years, with the peak incidence occurring between ages 6 and 10 years.

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

History

The typical patient is young and from an endemic area and has been exposed to infected persons with active disease.

Physical

Yaws has 3 clinical stages: primary, secondary, and tertiary. Stages are interspersed with asymptomatic latent periods.

• Primary stage
• • After an incubation period of 9-90 days (with an average of 3 wks), the primary lesion, or the mother yaw, develops at the site of inoculation after a scratch, a bite, or an abrasion of exposed skin, most commonly on the legs, the feet, or the buttocks.
  • The lesion is a reddish, nontender, and, occasionally, pruritic papulonodule.
  • The mother yaw ulcer develops a honey-brown crust and enlarges horizontally to 1-5 cm in diameter, sometimes coalescing with satellite lesions. The crust frequently sloughs off and reveals a raspberrylike base (hence the synonym frambesia).
  • On rare occasions, a primary lesion is not seen.
  • Because the exudate of the raspberrylike ulcer is teeming with treponemes, these lesions are considered highly infectious.
  • Lymphadenopathy, fever, and joint pain may accompany this stage.
  • The mother yaw resolves spontaneously in 2-9 months, leaving an atrophic scar with central hypopigmentation and peripheral hyperpigmentation.
• Secondary stage
• • Following a period of latency (about 6-16 wk after the primary stage), an eruption of disseminated skin lesions, bone lesions, and constitutional symptoms appears.
  • The cutaneous lesions, or the daughter yaws, resemble the mother yaw but are smaller (up to 2 cm in diameter) and are frequently located adjacent to body orifices, particularly the mouth and the nose.
  • The daughter yaws expand, ulcerate, and exude a fibrinous fluid teeming with treponemes, which dries into a crust. The exudate attracts flies, which are bothersome to the person who is affected.
  • Occasionally, central resolution yields circinate or annular scaly lesions resembling fungal infections. These lesions are referred to as tinea yaws.
  • Papulosquamous patches and plaques that resemble syphilis may be noted on any part of the body.
  • Lesions in the axillae or the groin resemble condylomata lata; lesions on the mucous membranes resemble hypertrophic mucous patches.
  • Piannic onychia is a paronychia caused by papillomas in the nail fold.
  • Papillomas on the plantar surfaces can form thick, hyperkeratotic plaques that may become fissured or eroded. Lesions are painful and cause a deliberate crablike gait (crab yaws). Macular and hyperkeratotic lesions on the palms and the soles resembling syphilis may also be present.
  • Skeletal involvement includes painful osteoperiostitis and fusiform soft tissue swelling of the metatarsals and the metacarpals. Some of the early bone changes can be seen on radiographs. Periosteal thickening can often be palpable.
  • Secondary-stage manifestations are generally nonscarring and reversible, subsiding in weeks to months.
  • Patients may develop relapses at intervals up to 5 years after infection. Relapsing lesions tend to occur in the perioral, perianal, and periaxillary areas. The disease then enters a noninfectious latent period, and patients do not exhibit any signs or symptoms.
• Tertiary stage
• • In about 10% of cases, after 5-15 years of latency, a late stage develops, characterized by destructive skin lesions, bone lesions, and possible neurologic and ophthalmologic involvement.
  • Progressively enlarging, painless, subcutaneous nodules develop, which undergo abscess formation, necrosis, and ulceration. Lesions have well-defined edges and an indurated base with granulation tissue and yellowish slough.
  • Ulcers may become infected, causing destruction of underlying structures. They may also coalesce, forming serpiginous tracts that heal with keloid formation, which leads to crippling deformities and contractures.
  • Hyperkeratosis and keratoderma of the palms and the soles as well as juxta-articular ulcerated gummatous nodules may accompany lesions.
  • Late skeletal lesions consist of hypertrophic periostitis, gummatous periostitis, osteitis, and osteomyelitis. Chronic osteitis of the tibia can lead to saber shins. In about 1% of patients, bilateral hypertrophic osteitis of the external aspects of the nasal processes of the maxillae with persistent swelling occurs. This condition is referred to as goundou, which slowly progresses over 5-20 years and eventually may lead to massive destruction and perforation of the nose and the palate (gangosa).
  • Neurologic and ophthalmologic involvement is debated in the literature. Some reports suggest that disc atrophy, optic atrophy, and myeloneuropathies may occur.
• Attenuated yaws
  • Some reports describe an attenuated, less contagious form of yaws in areas of low disease prevalence.
  • A solitary patch or a few, dry, flat, gray patches confined to the skin folds characterize attenuated yaws.

Causes

Yaws is caused by T pallidum subsp pertenue, a slender spirochete, which is serologically and morphologically indistinguishable from the spirochete that causes syphilis (T pallidum). Like the other nonvenereal treponematoses, yaws is not found in urban centers, it is not sexually transmitted, and it is not congenitally acquired. Children serve as the primary reservoir for yaws, spreading the disease via skin-to-skin and skin-to-mucous membrane contact.

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Other Problems to be Considered

Differential diagnoses of skin lesions
Idiopathic keratoderma
Calluses
Arthropod bites
Vitamin deficiencies

Differential diagnoses of nasopharyngeal lesions
Rhinosporidiosis
Rhinoscleroma
Tuberculosis
South American blastomycosis
Mucocutaneous leishmaniasis
Nasopharyngeal carcinoma
Noma

Differential diagnoses of bone lesions
Venereal or endemic syphilis
Tuberculosis
Osteomyelitis
Sickle cell anemia

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Lab Studies

• Microscopy: Diagnosis is made by clinical evaluation of lesions and confirmed by detection of treponemes on dark-field microscopy of serum obtained by squeezing the bases of the lesions.
• Serologic tests
• • Serologic tests are identical to those for venereal syphilis, including rapid plasma reagent (RPR) test, Venereal Disease Research Laboratory (VDRL) test, fluorescent treponemal antibody absorption (FTA-ABS) test, T pallidum immobilization (TPI) test, and T pallidum hemagglutination assay (TPHA).
  • RPR and VDRL tests are reactive 2-3 weeks after the onset of the primary lesion; they generally remain reactive throughout all stages.
  • No serologic test can distinguish yaws from other nonvenereal treponematoses; therefore, diagnosis is ultimately based on correlation of the clinical findings, epidemiologic history, and positive serologic results that are suggestive of yaws.

Imaging Studies

• Radiologic studies are nonspecific but can include any of the following findings:
• • Surface striations (periostitis)
  • Cortical thickening with bowing (saber shin deformity)
  • Spiculated periosteal reaction
  • General osseous expansion
  • Gummatous destruction
  • Draining sinuses
  • Epiphyseal separation
  • Stellate frontal bone scans

Histologic Findings

Histologic findings in early yaws include acanthosis, papillomatosis, and spongiosis. Neutrophilic exocytosis with intraepidermal microabscess formation is the most characteristic finding. The dermis has a moderate-to-dense granulomatous infiltrate mainly composed of plasma cells and lymphocytes with few histiocytes, neutrophils, and eosinophils. Unlike syphilis, endothelial proliferation is absent or low.

Late yaws has histologic findings similar to that of tertiary syphilis, including an intense dermal infiltrate composed of epithelioid cells, giant cells, lymphocytes, and fibroblasts. Caseation necrosis can also be observed. Plasma cells and histiocytes, in contrast to early yaws, are scarce.

Silver stains (Steiner) can be used to identify numerous treponemes between keratinocytes in early yaws. They are seen in a bandlike pattern or in clusters in the epidermis. Unlike T pallidum, which is found in both the epidermis and the dermis, T pallidum subsp pertenue is almost entirely epidermotropic.

Electron microscopy of early lesions demonstrates scarce treponemes in clusters in the intercellular spaces of the epidermis among inflammatory cells, within the cytoplasm of macrophages, and in the dermis.

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Medical Care

Treatment consists of appropriate antibiotic therapy. Penicillin remains the drug of choice for yaws. Tetracycline, erythromycin, or doxycycline should be considered for patients allergic to penicillin.

• Epidemiological treatment recommendations for yaws are as follows:
• • If greater than 50% of children are seropositive (hyperendemic), treat the entire population.
  • If 10-50% of children are seropositive (mesoendemic), treat active cases, contacts, and all children aged 15 years or younger.
  • If less than 10 of children are seropositive (hypoendemic), treat active cases, household members, and other obvious contacts.

MEDICATION

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Penicillin remains the drug of choice for yaws. No resistant strains of T pallidum have been reported; however, in 1988, Backhouse and colleagues, while monitoring an outbreak of yaws in children on Karkar Island, Papua New Guinea, found evidence suggestive of resistant strains. Approximately 28% of children treated with penicillin developed clinical and/or serologic evidence of relapse or reinfection. This finding suggests that some strains of T pallidum subsp pertenue may have reduced susceptibility or increased tolerance to penicillin treatment. Nonetheless, according to the 1980 WHO Scientific Group on Treponemal Infections, penicillin is the recommended treatment.

Drug Category: Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

FOLLOW-UP

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

Complications

• Unless treated, yaws can become a chronic, relapsing disease with skin, bone, and joint involvement. In 10% of cases, patients enter a late stage (tertiary stage) characterized by destructive cutaneous lesions and severely deforming bone and joint lesions. Neurologic and ophthalmologic involvement may also occur.

Prognosis

• Patients may develop relapses at intervals up to 5 years after infection.
• In 10% of patients, a late stage (tertiary stage) develops after 5-15 years. This stage is characterized by destructive skin lesions, bone lesions, and possible neurologic and ophthalmologic involvement (see Physical).

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• References

• Backhouse JL, Hudson BJ, Hamilton PA, Nesteroff SI. Failure of penicillin treatment of yaws on Karkar Island, Papua New Guinea. Am J Trop Med Hyg. Sep 1998;59(3):388-92. [Medline].
• Engelkens HJ, ten Kate FJ, Judanarso J, Vuzevski VD, van Lier JB, Godschalk JC, et al. The localisation of treponemes and characterisation of the inflammatory infiltrate in skin biopsies from patients with primary or secondary syphilis, or early infectious yaws. Genitourin Med. Apr 1993;69(2):102-7. [Medline].
• Farnsworth N, Rosen T. Endemic treponematosis: review and update. Clin Dermatol. May-Jun 2006;24(3):181-90. [Medline].
• Koff AB, Rosen T. Nonvenereal treponematoses: yaws, endemic syphilis, and pinta. J Am Acad Dermatol. Oct 1993;29(4):519-35; quiz 536-8. [Medline].
• Lupi O, Madkan V, Tyring SK. Tropical dermatology: bacterial tropical diseases. J Am Acad Dermatol. Apr 2006;54(4):559-78; quiz 578-80. [Medline].
• Rothschild BM, Heathcote GM. Characterization of the skeletal manifestations of the treponemal disease yaws as a population phenomenon. Clin Infect Dis. Aug 1993;17(2):198-203. [Medline].
• Sanchez MR. Endemic (Nonvenereal) Treponematoses. In: Freedberg IM, Eisen AZ, Wolff K, Austen F, Goldsmith LA, Katz S, eds. Fitzpatrick's Dermatology in General Medicine. 6^th ed. New York, NY: McGraw-Hill; 2003.
• Sehgal VN, Jain S, Bhattacharya SN, Thappa DM. Yaws control/eradication. Int J Dermatol. Jan 1994;33(1):16-20. [Medline].

Article Last Updated: Mar 23, 2007