What are the treatment options for chorioretinitis secondary to Histoplasmosis?

Treatment Options for Chorioretinitis Secondary to Histoplasmosis

Antifungal therapy is not recommended for presumed ocular histoplasmosis syndrome (POHS) as it has not shown efficacy and is not indicated according to clinical practice guidelines. 1

Understanding Ocular Histoplasmosis

Presumed ocular histoplasmosis syndrome (POHS) is a distinct chorioretinal disorder characterized by:

• Multiple small, punched-out peripheral chorioretinal scars
• Peripapillary atrophy
• Potential for choroidal neovascularization (CNV) development
• Typically affects young to middle-aged adults

Despite its name, the direct causative relationship with Histoplasma capsulatum remains controversial. The Infectious Diseases Society of America (IDSA) guidelines specifically list "presumed ocular histoplasmosis syndrome" under conditions where antifungal treatment is "not recommended, unknown efficacy or ineffective." 1

Treatment Algorithm for POHS

1. For Inactive Lesions (No CNV)

• Observation only
• Regular self-monitoring with Amsler grid
• Patient education about symptoms of CNV activation
• Periodic ophthalmologic follow-up

2. For Active Choroidal Neovascularization

First-line treatment:

• Anti-vascular endothelial growth factor (anti-VEGF) therapy 2
  • Intravitreal injections
  • Frequency determined by ophthalmologist based on disease activity

Location-based treatment options:

• Extrafoveal CNV:

  • Laser photocoagulation may be considered 2

• Juxtafoveal or subfoveal CNV:

  • Anti-VEGF therapy is preferred
  • Photodynamic therapy (PDT) may be considered as alternative or adjunctive treatment 2
  • Combination therapy (anti-VEGF + PDT) in selected cases

3. Monitoring and Follow-up

• Regular ophthalmologic examinations with OCT imaging to monitor disease activity
• Frequency determined by disease activity and treatment response
• Self-monitoring with Amsler grid between visits

Important Considerations

Differential Diagnosis

It's critical to distinguish POHS from other causes of chorioretinitis, particularly:

• Multifocal choroiditis (MFC), which may initially masquerade as POHS 3
• Toxoplasmic chorioretinitis, which requires specific antimicrobial therapy 1, 4

Testing Recommendations

• Histoplasma antigen/antibody testing (often negative in POHS) 3
• Serology panel to rule out autoimmune and infectious causes
• Fluorescein angiography and OCT to confirm active inflammation or CNV

Risk Reduction Strategies

For patients with confirmed POHS:

• Avoid LASIK surgery as it may trigger CNV 5
• Consider treatment of concurrent fungal infections (dermatomycoses, onychomycosis, vaginal candidiasis) which may potentially reduce risk of lesion reactivation 5

Special Situations

Recurrent or Refractory Disease

For cases initially diagnosed as POHS but with recurrent inflammation despite appropriate treatment:

• Consider alternative diagnoses such as multifocal choroiditis
• In confirmed MFC cases, immunomodulatory therapy may be considered 3

Pregnancy Considerations

• Anti-VEGF therapy should be used cautiously during pregnancy
• Treatment decisions should be made jointly by ophthalmologist, infectious disease specialist, and obstetrician

Key Pitfalls to Avoid

1. Misdiagnosis of toxoplasmic chorioretinitis as POHS (toxoplasmosis requires specific antimicrobial therapy)
2. Inappropriate use of antifungal agents for POHS (not effective per IDSA guidelines) 1
3. Delayed treatment of active CNV (can lead to permanent vision loss)
4. Failure to monitor for disease progression or recurrence

Remember that while POHS is associated with Histoplasma capsulatum exposure, antifungal therapy has not shown efficacy in treatment or prevention of recurrences, and management should focus on controlling CNV when present.