Marcia Ramos-e-Silva, MD, PhD

Associate Professor of Dermatology - Oral Dermatology Clinic Supervisor, HUCFF-UFRJ, School of Medicine, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

Poxviruses are the largest DNA viruses that affect animals. Humans may host three types: 1. orthopoxvirus, agents of variola or smallpox, and vaccinia; 2. parapoxvirus, producers of orf or ecthyma contagiosum, and milker's nodules; and 3. an unclassified group that includes molluscum contagiosum and tanapox, a virus only reported in Kenya and Zaire.

Smallpox, a highly contagious and fatal disease, disappeared after very intense worldwide vaccination campaigns, coordinated by the World Health Organization. No cases occurred since October 1977 and WHO declared it eradicated in the early 80's.

Oral manifestations of the other poxvirus diseases, although theoretically possible, are not very easily found. There are few reports of oral vaccinia after immunization, in humans, and of molluscum contagiosum, in AIDS patients. Goats and sheep may present oral ecthyma contagiosum.

MOLLUSCUM CONTAGIOSUM

DEFINITION: Molluscum contagiosum is a benign tumor-like viral disease seen in children. In adults it is sexually transmitted and frequently associated to AIDS infection.

ETIOLOGY: The disease is caused by one of the largest pox virus (200 by 300nm), called molluscum contagiosum virus, which has two subtypes: MCV-1 and MCV-2. Lesions caused by both subtypes are indistinguishable: MCV-1 is very frequent and has a worldwide distribution, while MCV-2 occurs mainly in HIV male patients. It does not grow in tissue cultures and the disease is not experimentally reproducible in other species.

PATHOGENESIS: Lesions are observed after an incubation period of seven to fifty days, and transmitted directly or through fomites. Autoinoculation is very common.

ORAL MANIFESTATIONS: Oral lesions are rare and reported in HIV patients. They are similar to cutaneous lesions and characterized by one to several 1 to 3mm persistent dome-shaped papules with a central umbilication. Giant elevations, with more than 1cm, are exceptional. The predilection sites are the lips, but the tongue and buccal mucosa may occasionally be affected.

ASSOCIATED FINDINGS: Mouth lesions are associated to HIV infection, decreased number and impaired function of T cells; but there are some reports on immunocompetent patients.

MICROSCOPIC FINDINGS: Histopathology shows a cup-shaped papule in the epidermis with a central opening, forming a keratin crater. Intracytoplasmic eosinophilic viral inclusions, typical of poxvirus and known as Handerson-Patterson or molluscum bodies, are observed inside keratinocytes.

DIAGNOSIS: Diagnosis of oral lesions is clinical, but a biopsy must be performed for confirmation.

DIFFERENTIAL DIAGNOSIS: Cryptococcosis, keratoacanthoma and warts in HIV patients can be clinically indistinguishable from molluscum contagiosum. Lymphangioma, hemangioma, pyogenic granuloma and condyloma acuminatum must also be considered. The final diagnosis has to be confirmed by histopathology.

TREATMENT: Curettage with or without diathermy is the choice method for the removal of the central viral core of the lesion. Cryosurgery is considered a good therapeutical option for widespread lesions and large lesions may require surgical excision.

BIBLIOGRAPHY
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5. ____. Pox viroses. In: Piérard GE, Caumes E, Franchimont C, Arrese Estrada JA. Dermatologie Tropicale. Brussels:Éditions de l'Université de Bruxelles. 1993:103-7.
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7. Highet AS, Kurtz J. Viral infections. In: Champion RH, Burton JL, Ebling FJG. eds. Rook, Wilkinson, Ebling Textbook of Dermatology. 5ed. London:Blackwell Scientific, 1992:867-951.
8. Knobler R. Human immunodeficiency virus infection. Dermatol Clin 1989;7(2):369-85.
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11. Lowy DR. Milker's nodules and molluscum contagiosum. In: Fitzpatrick TB, Eisen AZ, Wolff K, Freedberg JM, Austen KF. Dermatology in General Medicine. 4ed. New York:McGraw-Hill, 1993:2606-10.
12. Praetorius-Clausen F. Rare oral viral disorders (molluscum contagiosum, localized keratoacanthoma, verrucae, condyloma acuminatum, and focal epithelial hyperplasia). Oral Surg Oral Med Oral Pathol 1972;34(4):604-18.
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Figure 1: Lip molluscum contagiosum in an HIV patient (Courtesy of Sonia Ferreira, Arley Silva Jr. & Sandra Torres, Brazil)
Figure 2: Lip molluscum contagiosum in an HIV patient (Courtesy of Arley Silva Jr. & Sonia Ferreira, Brazil)

VACCINIA - COWPOX

DEFINITION: Vaccinia is the disease caused by a poxvirus (Poxvirus officinalis) used for smallpox vaccination. After smallpox eradication specific vaccination is now indicated only for special risk groups. The natural evolution of uncomplicated vaccination is limited by the host immune response and characterized by a local infection which heals with scarring.

ETIOLOGY: Poxvirus officinalis does not occur naturally and could be a mutant of smallpox or more likely of cowpox virus. This last virus is the agent of a cattle's disease which begins as papules, changes into vesicles and finally into pustules, providing immunity to smallpox virus in humans.

PATHOGENESIS: Vaccinia is a complication of smallpox vaccination that may happen in the same person or in an individual who had close contact with a recently vaccinated person. It may appear through three basic mechanisms: secondary bacterial infection, exaggerated viral replication, and altered reactivity to the virus.

ORAL MANIFESTATIONS: Oral lesions are mostly due to accidental inoculation and are similar to a normal smallpox vaccination. It begins as an erythematous nodule which turns into umbilicated vesicles, and small pustules. It can also be present as white plaques similar to diphtheric membrane. The only difference is that they do not tend to leave scars in the mouth.

ASSOCIATED FINDINGS: Other forms of this disease may be associated to mouth lesions, such as generalized vaccinia and eczema vaccinatum.

MICROSCOPIC FINDINGS: Histopathology shows ballooning or reticular degeneration of keratinocytes, epidermal necrosis, and dermal inflammatory infiltrate.

DIAGNOSIS: Recent history of vaccination or contact with a vaccinated person imposes the possibility of vaccinia. Positive Tzanck test, serology or viral culture are required for confirmation.

DIFFERENTIAL DIAGNOSIS: Accidental vaccinia must be differentiated from diseases that cause similar lesions, such as other viral infections, diphtheria, syphilis, herpes simplex, and aphthous stomatitis.

TREATMENT: Oral lesions after accidental inoculation are self-limited and do not require treatment. They usually heal spontaneously in seven to ten days without scarring. Hyperimmune serum against vaccinia may be necessary for more severe cases.

BIBLIOGRAPHY
1. Fulginiti VA. Smallpox and complications of smallpox vaccination. In: Fitzpatrick TB, Eisen AZ, Wolff K, Freedberg JM, Austen KF. Dermatology in General Medicine. 4ed. New York:McGraw-Hill, 1993:2596-602.
2. Greer KE, Sheap CN. A family outbreak of oral accidental vaccinia. Arch Dermatol 1974;110(1):107-8.
3. Gundersen SG, Bjorvatn B. Vaccinia and topical steroids: a case report. Acta Derm Venereol (Stockh) 1980;60(5):445-7.
4. Highet AS, Kurtz J. Viral infections. In: Champion RH, Burton JL, Ebling FJG. eds. Rook, Wilkinson, Ebling Textbook of Dermatology. 5ed. London:Blackwell Scientific, 1992:867-951.
5. Caumes E. Pox viroses. In: Piérard GE, Caumes E, Franchimont C, Arrese Estrada JA. Dermatologie Tropicale. Brussels:Éditions de l'Université de Bruxelles. 1993:104-7.

Figure 1: Oral vaccinia (Courtesy of Kenneth Greer & Christopher Sheap, USA)
Figure 2: Oral vaccinia (Courtesy of Kenneth Greer & Christopher Sheap, USA)