eMedicine Specialties > Ophthalmology > Retina

Presumed Ocular Histoplasmosis Syndrome

Author: Lihteh Wu, MD, Consulting Surgeon, Department of Ophthalmology, Vitreo-Retinal Section, Instituto De Cirugia Ocular, Costa Rica
Coauthor(s): Teodoro Evans, MD, Retina Fellow, Vitreo-Retinal Section, Instituto De Cirugia Ocular, Costa Rica
Contributor Information and Disclosures

Updated: Jul 24, 2007

Introduction

Background

Presumed ocular histoplasmosis syndrome (POHS) is a distinct clinical entity that is characterized by peripheral atrophic chorioretinal scars, peripapillary scarring, and maculopathy. This condition is believed to be secondary to exposure to Histoplasma capsulatum, although this fungus rarely has been isolated or cultured from an eye with the typically associated clinical findings.

Epidemiologic findings link the fungus to this condition. Based on skin tests in the United States, a similar geographic distribution of the fungal infection and POHS exists. Histoplasmin skin testing may exacerbate the ocular condition. Visual loss in POHS is secondary to the development of macular choroidal neovascularization (CNV).

Pathophysiology

H capsulatum is a dimorphic pathogenic fungus that often grows in soil around old chicken houses and areas harboring bats, such as caves. Large numbers of spores are dispersed into the air when contaminated soil is disturbed (eg, spelunking, raking). Exposure occurs when spores are inhaled.

In a normal host, the initial infection is usually asymptomatic or feels like influenza. In a few patients, a chronic cavitary pulmonary disease may follow. In immunocompromised patients, a progressive, life-threatening, disseminated form can occur. Following initial infection, hematogenous spread to the rest of the body, including the eye, can occur. A focal granulomatous choroiditis is thought to occur. This phase seldom is observed in humans.

In an experimental nonhuman primate model, inoculation of the organism via the carotid artery results in an active choroiditis. These foci are observed as discrete, round, yellowish choroidal lesions. Six weeks following inoculation of the organisms, isolating the organisms by any histologic techniques was not possible. The inflammatory response probably destroyed the invading organisms. With time, the lesions resolve, leaving the typical "punched-out" atrophic scars that disrupt the Bruch membrane (see Physical). Reexposure to the histoplasmin antigen may account for the enlargement of old scars and the emergence of new scars.

Visual loss in POHS is secondary to the development of CNV. Recently, pigment epithelium derived factor (PEDF) was found to have an inhibitory effect on ocular neovascularization. Another peptide, vascular endothelium growth factor (VEGF), is a well-known ocular angiogenic factor. The balance between antiangiogenic factors (eg, PEDF) and angiogenic factors (eg, VEGF) may determine the growth of CNV. This CNV usually grows in the subretinal space in a sheetlike fashion, not in the sub–retinal pigment epithelium (RPE) space. As the CNV grows, reactive hyperplastic RPE tries to surround and envelop the CNV. If successful, the CNV usually involutes.

Why CNV arises is unclear. Based on a case of a pregnant woman who developed a macular detachment during the third trimester, some propose that a type of vascular decompensation caused the CNV. A lymphocytic choroidal infiltrate usually is found near histo spots. Some hypothesize that an allergic reaction to Histoplasma antigens is an important stimulus for CNV growth. A few propose that the infectious granuloma secondary to the fungus is responsible for CNV growth. Others state that damage to the Bruch membrane by itself is a strong stimulus for CNV.

Frequency

United States

This condition occurs in endemic areas of the United States, including the Ohio and Mississippi River Valleys (Indiana, Ohio, Illinois, Kentucky, Tennessee, and Mississippi) and parts of the mid-Atlantic region (Maryland, West Virginia, and Virginia). Approximately, 200,000-500,000 new infections occur annually.

In an endemic area, 90% of patients with POHS had a positive histoplasmin skin test. In Maryland, 4% of those infected with histoplasmosis had POHS.

Peripheral atrophic scars were present in 2% of people living in endemic areas; disciform scars were found in 0.1% of people.

A clinical entity indistinguishable from POHS has been reported in a series of 10 patients from a nonendemic area, the Pacific Northwest. These patients tested negative to a lymphocyte stimulation assay with H capsulatum. Unlike series from the Midwest, all patients were female; 50% of them were myopic. The authors speculate that an atypical mycobacteria might be responsible for this entity.

International

H capsulatum is endemic in the Caribbean and Central and South America. No reports of POHS from these areas have appeared in the literature.

In the Netherlands and the United Kingdom, a clinical syndrome indistinguishable from POHS has been described. In the Dutch series by Suttorp-Schulten et al, a large number of female and myopic patients were reported.26 Given that H capsulatum is not found in Europe, some European colleagues have proposed to change the name from POHS to multifocal choroidopathy.

Mortality/Morbidity

  • POHS is an uncommon cause of visual loss.
  • The incidence and the prevalence in the blind population in Tennessee were reported to be 2.8% and 0.5%, respectively.

Race

  • Histoplasmin skin testing reveals that African Americans and Caucasians living in endemic areas are infected equally by H capsulatum. No difference is apparent between the prevalence of peripheral histo spots between these 2 groups. Caucasian patients are more likely than African Americans to develop macular CNV.
  • Some reports suggest an increased prevalence of POHS in patients with human leukocyte antigen B7 (HLA-B7) and human leukocyte antigen DRw2 (HLA-DRw2). Patients with HLA-DRw2 are more likely to have peripheral histo spots and disciform scarring, whereas patients with HLA-B7 are more likely to have peripheral histo spots.

Sex

  • No apparent gender predilection exists in the Midwest and the mid-Atlantic series according to Smith et al.25
  • In the series from the Netherlands by Suttorp-Schulten et al and in the series from the Pacific Northwest by Watzke et al, women seemed to be affected to a greater degree.26,27

Age

  • This condition usually affects patients aged 20-50 years; the average age is 35 years.

Clinical

History

  • Residents or visitors to endemic areas
  • Prior exposure to chickens, parakeets, or pigeons
  • Distorted vision
  • Sudden, painless loss of central visual acuity
  • Micropsia
  • Positive scotoma
  • Asymptomatic

Physical

  • Both the vitreous and the anterior chamber are typically clear because of a lack of intraocular inflammation.
  • Punched-out chorioretinal scars (smaller in size than the optic nerve) are called histo spots. Black pigment may appear within or at the margins of these lesions. Linear streaks of atrophic scars in the mid periphery are observed in about 5% of patients with POHS.
  • Peripapillary chorioretinal scarring is present.
  • Macular CNV usually is observed as a gray-green subretinal lesion that is surrounded by subretinal blood and leads to a serous or hemorrhagic macular detachment. CNV is estimated to occur in 5% of eyes affected with POHS.

Causes

The cause of this condition is H capsulatum.

More on Presumed Ocular Histoplasmosis Syndrome

Overview: Presumed Ocular Histoplasmosis Syndrome
Differential Diagnoses & Workup: Presumed Ocular Histoplasmosis Syndrome
Treatment & Medication: Presumed Ocular Histoplasmosis Syndrome
Follow-up: Presumed Ocular Histoplasmosis Syndrome
References
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References

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  8. Gass JD. Stereoscopic Atlas of Macular Diseases. In: Diagnosis and Treatment. 4th ed. St Louis: Mosby Year Book Inc; 1997:130-147.

  9. Godfrey WA, Sabates R, Cross DE. Association of presumed ocular histoplasmosis with HLA-B7. Am J Ophthalmol. Jun 1978;85(6):854-8. [Medline].

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  24. Smith RE, Dunn S, Jester JV. Natural history of experimental histoplasmic choroiditis in the primate. I. Clinical features. Invest Ophthalmol Vis Sci. Jul 1984;25(7):801-9. [Medline].

  25. Smith RE, Ganley JP. An epidemiologic study of presumed ocular histoplasmosis. Trans Am Acad Ophthalmol Otolaryngol. Sep-Oct 1971;75(5):994-1005. [Medline].

  26. Suttorp-Schulten MS, Bollemeijer JG, Bos PJ, Rothova A. Presumed ocular histoplasmosis in The Netherlands--an area without histoplasmosis. Br J Ophthalmol. Jan 1997;81(1):7-11. [Medline].

  27. Watzke RC, Klein ML, Wener MH. Histoplasmosis-like choroiditis in a nonendemic area: the northwest United States. Retina. 1998;18(3):204-12. [Medline].

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Further Reading

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Keywords

POHS, ocular histoplasmosis, peripheral atrophic chorioretinal scars, peripapillary scarring, maculopathy, Histoplasma capsulatum, H capsulatum, histoplasmin skin testing, fungal infection, macular choroidal neovascularization, macular CNV, vision loss

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Contributor Information and Disclosures

Author

Lihteh Wu, MD, Consulting Surgeon, Department of Ophthalmology, Vitreo-Retinal Section, Instituto De Cirugia Ocular, Costa Rica
Lihteh Wu, MD is a member of the following medical societies: American Academy of Ophthalmology, American Society of Retina Specialists, Association for Research in Vision and Ophthalmology, and Pan-American Association of Ophthalmology
Disclosure: Nothing to disclose.

Coauthor(s)

Teodoro Evans, MD, Retina Fellow, Vitreo-Retinal Section, Instituto De Cirugia Ocular, Costa Rica
Disclosure: Nothing to disclose.

Medical Editor

Russell P Jayne, MD, Consulting Vitreoretinal Surgeon, The Retina Center at Las Vegas
Russell P Jayne, MD is a member of the following medical societies: American Medical Association, American Society of Cataract and Refractive Surgery, and American Society of Retina Specialists
Disclosure: Nothing to disclose.

Pharmacy Editor

Simon K Law, MD, PharmD, Assistant Professor of Ophthalmology, Jules Stein Eye Institute; Chief of Section of Ophthalmology Surgical Services, Department of Veterans Affairs Healthcare Center, West Los Angeles
Simon K Law, MD, PharmD is a member of the following medical societies: American Academy of Ophthalmology, American Glaucoma Society, and Association for Research in Vision and Ophthalmology
Disclosure: Nothing to disclose.

Managing Editor

Steve Charles, MD, Director of Charles Retina Institute; Clinical Professor, Department of Ophthalmology, University of Tennessee College of Medicine
Steve Charles, MD is a member of the following medical societies: American Academy of Ophthalmology, American Society of Retina Specialists, Macula Society, and Retina Society
Disclosure: Alcon Laboratories Consulting fee Consulting

CME Editor

Lance L Brown, OD, MD, Ophthalmologist, Affiliated With Freeman Hospital and St John's Hospital, Regional Eye Center, Joplin, Missouri
Disclosure: Nothing to disclose.

Chief Editor

Hampton Roy Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences
Hampton Roy Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, and Pan-American Association of Ophthalmology
Disclosure: Nothing to disclose.

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