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L8
HHV6
D. Haider
Human herpes virus type 6:
A lymphotropic virus and the single commonest cause of hospital visits in infants with fever.
The cause of roseola.
Human herpesvirus type 7:
Epidemiology:
First demonstrated in 1990 from peripheral blood mononuclear cells of a healthy adults. Its role
in human disease is yet to be defined.
Pathogenesis:
Very similar to HHV-6;it is a lymphotropic virus that infect CD4 T cells and encode genes
allowing it to invade the immune system.
Clinical Features:
1- Generally asymptomatic. Probably causes similar fever and rash syndromes to HHV-6.
2- IT may be a cofactor for symptomatic CMV disease in renal transplant recipients.
Human herpesvirus type 8:
A herpesvirus associated with several human neoplasms, including Kaposi sarcoma (KS),
primary effusion lymphoma, and Castleman disease.
THE VIRUS:
A gamma-herpesvirus (like EBV),first identified in KS tissue from patients infected with HIV.
Epidemiology:
1. In 1980, clusters of KS amongst homosexual men contributed to the recognition of HIV
.It has also seen in renal transplant recepients.HHV-8 has been identified in lesions from
all forms of KS.
2. Over 95% of HIV-associated KS, cases are in homosexual men, in whom it is up to 15
times commoner than in those acquiring HIV non-sexually.
3. Epidemiological studies suggests a sexual route of HHV-8 transmission, but other means
of transmission are not clear.HHV-8 DNA has been detected in the semen and saliva of
HIV-infected patients with KS, and not healthy controls.
Clinical Features of Herpesviruses-Type 8:
1) Primary infection: may be associated with fever and rash in children, and new onset
lymphadenopathy has been described in HIV-negative homosexual men undergoing
HHV-8 seroconversion. Fever, splenomegaly, pancytopenia, and rapid-onset KS has been
described in immunocompromised patients.
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2) KS:four
epidemiological
types:classic,endemic.HIV-ssociated,transplant-
associated).and appear on skin, mucous membranes and viscera(lung,and biliary tract
particularly).Lesions are highly vascular and nodular(o.5 cm-2 cm in diameter).
Violacious or brown/black in pigmented skin. Visceral disease may involve any
organ(e.g.GI can bleed, pulmonary-effusions).Lymphedema may follow regional lymph
node infilteration.Endemic KS is slow growing and has little prognostic significance. In
AIDS patients with KS ,the health impact of the lesion is generally of less importance
than opportunistic infections.
3) Primary effusion lymphoma(PEL):an aggressive B-cell lymphoma seen in AIDS patients,
with predilection for a body cavities, presents as lymphomatous effusions, arising
predominantly in the pleural, pericardial and peritoneal cavities.
4) Castlemans disease: an uncommon lymphoproliferative disorders, first described in
1950.Localized(Unicentric ,UCD) FORMS ARE BENIGN AND MAY BE CURED
BY SURGICAL EXCISION.Multicentric castleman disease(MCD) is associated with
HIV, and is aggressive and is often fatal.
HHV-8 is associated with less than 50% of HIV-negative MCD and 100% of HIV-
positive MCD.
Diagnosis:
1. Diagnosis of KS is clinical and confirmed by biopsy.
2. Lesion biopsy is required for the diagnosis of PEL and Castleman disease.
3. Serology is of limited clinical utility.
4. PCR for HHV-8 is of little benefit in the diagnosis of KS BECAUSE VIREMIA IS NOT
UNIVERSAL WHILE IT IS SO USEFUL IN THE DIAGNOSIS OF MCD,because
patients with active disease is viremic and quantification of HHV-8 IS used to track
response to treatment.
Mubark A. Wilkins