Human Herpesvirus 6 (HHV-6): Clinical Syndromes and Disease Associations

Virology & Epidemiology

HHV-6 (Roseolovirus) has two variants: HHV-6A (neurotropic, less common) and HHV-6B (ubiquitous, causes roseola). >90% seroprevalence by age 2; latency in salivary glands, monocytes, CNS.

Primary Infection Syndromes

• Exanthem subitum (Roseola infantum / Sixth disease): High fever (3–5 d) → defervescence + macular/papular rash (trunk → extremities); febrile seizures common. Self-limited.
• Asymptomatic: Majority.
• Atypical: Hepatitis, thrombocytopenia, encephalitis (rare).

Reactivation / Chronic Associations

HHV-6 reactivates in immunocompromised (transplant, HIV) → encephalitis, pneumonitis, bone marrow suppression, graft rejection.

Controversial Links (Association ≠ Causation)

• Multiple sclerosis: HHV-6 DNA in plaques; molecular mimicry hypothesized.
• Chronic fatigue syndrome (ME/CFS): Elevated titers in subsets; not diagnostic.
• Fibromyalgia, Alzheimer's, Parkinson's: Viral DNA/antigens detected in some CNS tissue; mechanistic role unproven.

Testing & Treatment

• PCR (blood, CSF, tissue) for active replication; serology for past exposure.
• Antivirals: Ganciclovir, foscarnet, cidofovir (for severe/reactivated disease in immunocompromised). No role in roseola.

HHV-6 is a common childhood virus with rare severe manifestations; its role in chronic neuroinflammatory diseases remains under investigation.