Background

Diffuse unilateral subacute neuroretinitis (DUSN) is a progressive parasitic disease affecting the outer retina and retinal pigment epithelium (RPE). This syndrome is primarily unilateral, although bilateral cases have occurred.^[1]DUSN has been reported to develop in association with other infectious processes such as catscratch disease caused by Bartonella henselae^[2] and herpes simplex virus type 2 infection.^[3] The ocular findings of DUSN include visual loss, vitreous cells, optic disc inflammation and leakage, and transient recurrent crops of gray-white outer retinal lesions.^{[4, 5, 6]}

Stationary or migrating nematodes have been identified deep in the retina or in the subretinal space. Later in the course of the disease, slowly progressive RPE changes and optic atrophy may be observed, as well as narrowing of the retinal vessels.

Pathophysiology

The exact pathophysiology is uncertain, but the local inflammatory changes may be related to toxic effects or immunologic stimulation from excretory products of the larva or from release of unknown soluble tissue toxins. The fleeting gray-white lesions in the outer retina appear to be a local reaction to noxious stimulation. The loss of vision and progressive optic atrophy secondary to death of ganglion cells and neural fibers may be a remote reaction to soluble toxins.

Frequency

United States

The southeast and the upper Midwest are known endemic areas for the disease.

International

DUSN was reported initially in the Caribbean islands, Brazil, Ghana, and Germany.^{[7, 8]} Since 2000, DUSN has been reported in many other countries, including China,^[9]India,^[10]South Africa, Spain, and Korea.^[11]

Mortality/Morbidity

No cases of mortality have been reported. Four cases of severe neurologic degeneration with DUSN have been reported in children.

The natural history of untreated DUSN involves multiple recurrent episodes of diffuse and focal inflammation of the retina and RPE with secondary progressive visual loss and optic atrophy in the affected eye.

It rarely affects the fellow eye. Only 2 cases with bilateral involvement have been reported.

Race

DUSN does not show any particular racial preference.

Sex

This condition occurs more frequently in males than in females.

Age

It occurs most frequently in the second and third decades. Young children and older adults also may be affected.

Clinical Presentation

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Author

Lakshmana M Kooragayala, MD Vitreo-retinal Surgeon, Marietta Eye Clinic

Lakshmana M Kooragayala, MD is a member of the following medical societies: American Academy of Ophthalmology, American Society of Retina Specialists

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

R Christopher Walton, MD Adjunct Professor, Department of Ophthalmology, University of Texas Health Science Center at San Antonio

R Christopher Walton, MD is a member of the following medical societies: American Academy of Ophthalmology, American Uveitis Society

Disclosure: Nothing to disclose.

Chief Editor

Andrew G Lee, MD Chair, Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital; Clinical Professor, Associate Program Director, Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch School of Medicine; Clinical Professor, Department of Surgery, Division of Head and Neck Surgery, University of Texas MD Anderson Cancer Center; Professor of Ophthalmology, Neurology, and Neurological Surgery, Weill Medical College of Cornell University; Clinical Associate Professor, University of Buffalo, State University of New York School of Medicine

Andrew G Lee, MD is a member of the following medical societies: American Academy of Ophthalmology, American Geriatrics Society, Houston Neurological Society, Houston Ophthalmological Society, International Council of Ophthalmology, North American Neuro-Ophthalmology Society, Texas Ophthalmological Association

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: AstraZeneca; Bristol Myers Squibb; Horizon<br/>Serve(d) as a speaker or a member of a speakers bureau for: Horizon<br/>Received ownership interest from Credential Protection for other.

Additional Contributors

Andrew A Dahl, MD, FACS Assistant Professor of Surgery (Ophthalmology), New York College of Medicine (NYCOM); Director of Residency Ophthalmology Training, The Institute for Family Health and Mid-Hudson Family Practice Residency Program; Staff Ophthalmologist, Telluride Medical Center

Andrew A Dahl, MD, FACS is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, American Intraocular Lens Society, American Medical Association, American Society of Cataract and Refractive Surgery, Contact Lens Association of Ophthalmologists, Medical Society of the State of New York, New York State Ophthalmological Society, Outpatient Ophthalmic Surgery Society

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous coauthor, James P Ganley, MD, PharmD, DrPH, to the development and writing of this article.