Can Human Herpesvirus 7 (HHV-7) cause acute anterior uveitis?

HHV-7 as a Cause of Acute Anterior Uveitis

While HHV-7 has been identified as an emerging cause of viral anterior uveitis, it has not been definitively documented to cause a specific disease and there is insufficient evidence to establish it as a common cause of acute anterior uveitis. 1

Viral Causes of Anterior Uveitis

Established Viral Pathogens

• Primary viral causes:

  • Herpes Simplex Virus (HSV)
  • Varicella-Zoster Virus (VZV)
  • Cytomegalovirus (CMV)
  • Rubella Virus

• Emerging viral causes:

  • Human Herpesvirus 6,7, and 8
  • West Nile Virus
  • HIV
  • Epstein-Barr Virus
  • Parechovirus
  • Dengue Virus
  • Chikungunya Virus 1

HHV-7 Specifically

According to CDC guidelines, "HHV-7 has not been definitively documented to cause a specific disease, with no apparent correlation between HHV-7 and HIV plasma load, suggesting that HHV-7 infection might not be stimulated by or interact with HIV infection." 2

Clinical Features of Viral Anterior Uveitis

Viral anterior uveitis should be suspected when the following features are present:

• Diffuse, fine, stellate keratic precipitates
• Iris atrophy
• Ocular hypertension 3, 4
• Unilateral involvement
• Recurrent episodes 4

Differential Patterns

1. HSV/VZV pattern:

   • Granulomatous cluster of small and medium-sized keratic precipitates in Arlt's triangle
   • Possible corneal scars
   • More acute disease process
   • Larger keratic precipitates 4, 5

2. VZV-specific features:

   • Severe intraocular inflammation
   • Severe aqueous flare
   • High viral load in aqueous humor
   • Segmental iris atrophy 5

3. CMV pattern:

   • Posner-Schlossman syndrome
   • Few medium-sized keratic precipitates
   • Minimal anterior chamber cells
   • Extremely high intraocular pressure
   • Mildest intraocular inflammation
   • Lowest corneal endothelial cell density 4, 5

4. Rubella pattern:

   • Fuchs uveitis syndrome
   • Fine stellate keratic precipitates diffusely distributed over corneal endothelium
   • Diffuse iris stromal atrophy without posterior synechiae
   • Onset in second to third decade
   • Posterior subcapsular cataract
   • Possible iris heterochromia
   • Often develops vitritis without macular edema 4

Diagnostic Approach

Due to the considerable overlap in clinical manifestations among different viral anterior uveitides, laboratory confirmation is often necessary:

1. Aqueous humor sampling:

   • Quantitative PCR for viral DNA
   • Goldmann-Witmer coefficient assay 4

2. Clinical examination:

   • Slit-lamp biomicroscopy to evaluate:
     • Keratic precipitates (size, distribution, appearance)
     • Iris atrophy
     • Anterior chamber reaction
     • Intraocular pressure 2

Treatment Considerations

• For HSV/VZV: Acyclovir remains the mainstay of therapy 3
• For CMV: Ganciclovir, though relapse rate is high and prolonged therapy may be required 3
• For HHV-7: No specific treatment recommendations exist due to lack of definitive disease association 2

Caution: Corticosteroids should be used carefully in suspected viral uveitis if specific viral diagnostic tests are not available, as they may worsen certain viral infections 3

Complications and Monitoring

• Common complications:

  • Cataract
  • Glaucoma 3
  • Corneal scarring
  • Vision loss

• Monitoring:

  • Regular intraocular pressure measurements
  • Corneal endothelial cell counts (especially with CMV)
  • Assessment for cataract development

Summary

While HHV-7 has been mentioned as an emerging potential cause of viral anterior uveitis in recent literature 1, there is currently insufficient evidence to definitively establish it as a common or well-characterized cause of acute anterior uveitis. The primary viral pathogens to consider in viral anterior uveitis remain HSV, VZV, CMV, and rubella virus, with their distinctive clinical patterns as described above.