| Presumed ocular histoplasmosis syndrome | |
|---|---|
| Classification and external resources | |
| DiseasesDB | 31279 |
| eMedicine | oph/406 |
Presumed ocular histoplasmosis syndrome (POHS) is a disease syndrome affecting the eye that is characterized by peripheral atrophic chorioretinal scars, atrophy or scarring adjacent to the optic disc and maculopathy.
The loss of vision in POHS is caused by choroidal neovascularization.
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It is thought to be caused by Histoplasma capsulatum, but the fungus has rarely been isolated from cases with POHS.
The word "presumed" is also emphasized because the condition has also been found in locations where histoplasmosis is rare.[1]
Fluorescein angiography is required for diagnosis and follow-up of patients with POHS.
Treatment requires careful consideration of FA findings and few cases may respond to corticosteroids and laser photocoagulation. A vitreo-retinal specialist should be consulted for proper management of the case.
Presumed ocular histoplasmosis syndrome and age-related macular degeneration (AMD) have been successfully treated by the drug Bevacizumab (trade name Avastin, Genentech/Roche).[2] Ophthalmologists are using Avastin "off-label"[3] to treat AMD and similar conditions since research indicates that vascular endothelial growth factor (VEGF) is one of the causes for the growth of the abnormal vessels that cause these conditions. Some patients treated with Avastin had less fluid and more normal-appearing maculas, and their vision improved. Avastin injections into the affected eye have been used by retina specialists since early 2005. Thus there is no long term 10 to 15 year follow up data for possible late complications.[4] Early treatment is critical to maintaining vision.
Other treatments include Ranibizumab (trade name Lucentis) which is approved by the FDA for intraocular use. Lucentis uses a smaller molecule compared to Avastin and according to GenenTech, the smaller molecule helps lower the systemic toxicity of the drug, thereby lowering the overall risks compared to Avastin.[5] However, Lucentis costs approximately $1,600 per injection compared to less than $100 per injection for Avastin. Research has shown[6] that Avastin and Lucentis to be equally effective in the treatment of POHS and AMD.
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