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Molluscum Contagiosum and Other Poxviruses, Excluding Smallpox Virus

Molluscum Contagiosum and Other Poxviruses, Excluding Smallpox Virus

Fred Wang

The poxviruses include a large number of related DNA viruses that infect various vertebrate hosts. The poxviruses responsible for infections in humans, along with the main manifestations of these infections, are listed in Table 1. Systemic human disease can result from infection with smallpox (variola major) virus, a poxvirus that infects only humans, or from zoonotic infection with monkeypox virus. Other poxvirus infections cause primarily localized skin disease in humans. Molluscum contagiosum virus (MCV) is an obligate human pathogen that causes distinctive proliferative skin lesions; molluscum contagiosum is the most frequent human disease resulting from poxvirus infection. Exposure to animals infected with other poxviruses can also cause localized skin disease in humans.

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Lyme Borreliosis

Lyme Borreliosis

Allen C. Steere

DEFINITION

Lyme borreliosis is caused by a spirochete, Borrelia burgdorferi, sensu lato, that is transmitted by ticks of the Ixodes ricinus complex. The infection usually begins with a characteristic expanding skin lesion, erythema migrans (EM; stage 1, localized infection). After several days or weeks, the spirochete may spread hematogenously to many different sites (stage 2, disseminated infection). Possible manifestations of disseminated infection include secondary annular skin lesions, meningitis, cranial or peripheral neuritis, carditis, atrioventricular nodal block, or migratory musculoskeletal pain. Months to years later (usually after periods of latent infection), intermittent or chronic arthritis, chronic encephalopathy or polyneuropathy, or acrodermatitis may develop (stage 3, persistent infection). Most patients experience early symptoms of the illness during the summer, but the infection may not become symptomatic until it progresses to stage 2 or 3. Despite regional variations, the basic stages of the illness are similar worldwide.

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Miscellaneous skin conditions

Miscellaneous skin conditions

Acanthosis nigricans

This is a relatively common condition, which may be a marker for insulin resistance and occasionally malignancy. Clinically, it presents as hyperpigmented, hyperkeratotic areas that are usually symmetrically distributed in the axillae, the groin, on the neck and in the cubital and popliteal fossae. Multiple skin tags are commonly associated. The mucosal surfaces and the back of the hands and feet may be involved, especially when associated with malignancy.

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Itch without rash

Itch without rash

Itching of the skin, or pruritus, may be associated with dermatological conditions, pregnancy, systemic illness or psychological disorders.

When itching is not associated with a rash, it is often difficult to identify its cause. Providing symptomatic relief only may meet a patient’s needs in the short term, but will not be in the patient’s best long-term interests unless a careful search for the cause of the itch is undertaken and the provoking factors dealt with wherever possible.

Persistent scratching of apparently normal skin will eventually produce a rash characterised by linear excoriations and/or lichen simplex chronicus, which will not resolve until the itch has been relieved.

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