Poxviridae Notes

Chapter 2 Acyanotic Defects NOTES POXVIRIDAE MICROBE OVERVIEW Genetic material ▪ Linear double-stranded DNA Replication ▪ In host cell cytoplasm Taxonomy ▪ Poxviridae: family of double-stranded DNA viruses Associated clinical syndromes ▪ Febrile rash illnesses: smallpox (eradicated), monkeypox ▪ Skin lesions: vesicles, pustules, papules, skin thickening Morphology ▪ Brick-shaped/ovoid ▪ Enveloped (outer lipid membrane) ▪ Size: 220–450nm MOLLUSCUM CONTAGIOSUM osms.it/molluscum-contagiosum PATHOLOGY & CAUSES ▪ Molluscum contagiosum virus (MCV): poxvirus; causes papular skin disease ▪ Four subtypes; genotype 1 causes most U.S. cases ▪ Common in children, adolescents ▪ Skin penetration → stratum spinosum replication within keratinocytes → epidermal hypertrophy → papules ▪ Incubation period: 2–6 weeks COMPLICATIONS ▪ Widespread/refractory lesions in immunosuppressed individuals CAUSES ▪ Physical contact, autoinoculation, fomites RISK FACTORS ▪ Contact sports; sexual intercourse with infected individuals; immunosuppression; atopic dermatitis Figure 91.1 The wart-like lesions caused by molluscum contagiosum infection. OSMOSIS.ORG 497

SIGNS & SYMPTOMS ▪ Dome-shaped, shiny, umbilicated papules (2–5 mm); sometimes polypoid ▪ Lesion distribution: trunk, genitals, intertriginous areas (e.g. axilla, antecubital folds); not on palms, soles ▪ Sometimes pruritus, inflammation, swelling ▪ Molluscum dermatitis: eczematous patches/plaques around papules ▪ Eyelid lesions → keratoconjunctivitis DIAGNOSIS Figure 91.2 A histological section through a molluscum wart at low power. There is marked acanthosis and marked hyperplasia causing inversion. LAB RESULTS ▪ Histologic examination: keratinocyte eosinophilic inclusion bodies (Henderson– Paterson bodies) OTHER DIAGNOSTICS ▪ Clinical examination: dermoscopy; polylobular, amorphous structures with central umbilication, peripheral blood vessels TREATMENT ▪ Optional; lesions resolve spontaneously in 6–18 months in immunocompetent individuals MEDICATIONS Chemical disruption ▪ Topical blistering agent: cantharidin ▪ Antimitotic agent: podophyllotoxin ▪ Topical immunomodulator: imiquimod ▪ Potassium hydroxide (KOH) ▪ Keratinolytic agent: salicylic acid Antiviral treatment ▪ Cidofovir SURGERY Lesion removal ▪ Cryotherapy, curettage, laser OTHER INTERVENTIONS Figure 91.3 A histological section through a molluscum wart at high power. The stratum spinosum and granulosum contain eosinophilic inclusions, known as molluscum bodies. 498 OSMOSIS.ORG Prevention ▪ Avoid sharing towels/clothing ▪ Cover lesions with bandage/clothing ▪ Barrier contraception (e.g. condoms)