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DNA VIRUSES

  1. Pox viruses

  2. Papillomaviruses

  3. Herpes viruses

  4. Parvoviruses

  5. Hepadnavirus

Pox Viruses

  • Large, enveloped, double-stranded, linear DNA viruses

  • Belong to the Poxviridae family

  • Replicate in the cytoplasm, except for the adenovirus

  • Poxviruses of clinical importance include smallpox, vaccinia, monkeypox, molluscum contagiosum, orf, and milkers' nodules

MOLLUSCIPOX (MOLLUSCUM CONTAGIOSUM; MCV)

  • Common, benign, self-limiting skin disease

  • Generally affects pediatric age group

  • Virus commonly acquired by skin-to-skin contact (nonsexual)

  • Incubation period is from 2 weeks to 6 months

  • Four different strains have been identified (based on restriction endonuclease digestion pattern). Two main subtypes: MCV I, responsible for the majority of infections in the United States, and MCV II (more prevalent in HIV patients); both are genital/nongenital

  • Clinical

    • 3- to 6-mm erythematous or skin-colored, dome-shaped, umbilical papules distributed over the trunk and face. The lesions may persist for 6 to 8 weeks or more (Fig. 17-1)

    • In immunocompromised patients, especially HIV-infected individuals, thousands of papules distributed on the body and face. High risk of bacterial infection and treatment resistance

    • Genital papules: usually sexually transmitted, most common in adults (Fig. 17-2)

    • Positive Koebner reaction

    • Free virus cores found in all layers of epidermis

  • Diagnosis

    • Clinical

    • Confirmatory biopsy in some cases. Henderson-Paterson bodies (molluscum bodies) = viral particles in infected keratinocytes, eosinophils

  • Treatment

    • Resolution is often preceded by inflammation, uncomplicated lesions heal without scaring

    • Physical destruction (salicylic acid, liquid nitrogen, cantharidin, lactic acid, CO2, trichloroacetic acid)

    • Immune modulation: imiquimod

    • Manual extrusion (curettage) of the lesions

    • Cidofovir in immunocompromised patients

FIGURE 17-1

Molluscum contagiosum. (Used with permission from Dr. Adelaide Hebert.)

FIGURE 17-2

Molluscum contagiosum genital. (Used with permission from Dr. Adriana Motta.)

SMALLPOX

  • Caused by variola virus; variola minor also known as alastrim

  • Serious, contagious, and sometimes fatal infectious disease

  • Eradicated after a successful worldwide vaccination program

  • Face-to-face contact is not required to be infected, direct contact with infected body fluids or contaminated objects

  • Humans are the only natural host

  • Clinical

    • Incubation 12 to 13 days, fever, malaise, backache, body aches, and exanthem that appears after 2 to 4 days

    • Two clinical forms: Variola major, most common and severe form with a 30% incidence of mortality (secondary to pulmonary edema from heart failure), 4 clinical types: ordinary, modified (by previous vaccination), flat, and hemorrhagic; and Variola minor, less severe and 1% mortality

    • Early rash appears as small red spots in the mouth; macules → papules → vesicles → pustules; all lesions exist in the same stage

    • Complications: corneal ulceration, laryngeal lesions, encephalitis, hemorrhage

    • Progressive vaccinia related to immunosuppression, malignancy, radiation therapy, or AIDS

  • Vaccination: rare postvaccinal encephalitis and progressive ...

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