Human Herpes Virus-8 Infections

• HHV8 is a gamma-herpesvirus that only naturally occurs in humans. There are no animal resevoirs.
• HHV8, in common with other HHVs, causes primary infection, latency for life (probably in leukocytes), and reactivation. However, relatively little is known about HHV8 compared to other HHVs.
  • This reflects that HHV8 was first isolated from Kaposi's Sarcoma tissue in 1994.
    • Until the AIDS epidemic became established in the early-mid 1980s, Kaposi's sarcomas were rare.
• Because of its role in the development of Kaposi's Sarcoma, HHV8 is currently being intensively investigated.
• Attempts to produce an effective vaccine against HHV8 infection have not been successful to date.
• HHV8 is of direct relevance to the practice of dentistry as:
  • HHV8 is infectious, but it remains unclear how infection is transmitted and whether this could occur in the dental environment.
    • Accordingly, good Cross Infection practices are essential.
  • Recognition of a Kaposi's Sarcoma should alert the clinician to the possiblity that the patient has HIV Infection or is immunocompromised in some other way.

Kaposi's Sarcoma

• Kaposi's sarcoma (KS) is characterised by a proliferation of abnormal vascular structures and has several different histopathological forms.
• KS was first described in 1872 by a Hungarian physician.
  • Subsequently, KS was recognised to be a rare, indolent tumour that most typically involved the leg skin of elderly Ashkenazi Jewish men.
• In the early 1980s, an increasing number of cases of KS were reported in young men. The association with AIDS, particularly as the CD4 count dropped, was soon established.
  • KS occasionally occur in other immuncompromised patients in the absence of HIV infection.
• KS can involve the skin, mucosa or internal viscera (e.g. G.I. tract or lungs).
• The natural history of a typical KS is as follows:
  • Starts as a small purple/red macule (i.e. a flat lesion) that is asymptomatic.
  • With time, the lesion may increase in size and become raised and tender.
  • Some lesions go on to become nodular, when they are particularly prone to painful ulceration.
• KS do not blanch when pressed.
• Because early KSs are asymptomatic, observation of an intraoral KS may be the first indication that the patient has HIV Infection.
  • One third of patients with AIDS-related KS have oral involvement at the time of presentation.
• Multiple KSs can develop concurrently.
  • Metastatic spread is rare, and some dispute that the term 'sarcoma' is appropriate for KS.
• KS rarely contribute directly to death, but they can cause troublesome symptoms, particularly pain when advanced, that can impact significantly on the quality of life.
• KS in AIDS diminish in size and can even resolve when HAART is taken.
  • However, HAART is expensive and is unavailable to the majority of those with AIDS.
• Many other treatments have been used in symptomatic KS including:
  • Cryotherapy, intralesional chemotherapy, laser therapy and radiotherapy.

A. Flat Kaposi's sarcomas involving the hard and soft palates. B. Nodular gingival Kaposi's sarcoma (arrows). Multiple skin Kaposi's sarcomas in a patient with advanced AIDS.

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