Authors: Michael R. Christensen, MS-IV, Virginia Commonwealth University School of Medicine; Charles Calvo, MD
Photographer: Moran Eye Center Photography
Keywords/Main Subjects: Choroideremia, Retina, dystrophy, X-linked
Brief Description: Choroideremia refers to an X-linked genetic chorioretinal dystrophy that results in atrophy of cells in the RPE, choroid, and outer retina.
Age & Gender: This is a condition that occurs almost exclusively in males, although female carriers can rarely be affected later in life. It generally presents in a male’s second or third decade and worsens dramatically in the sixth or seventh decade.
Genotype: X-linked mutations in the CHM gene which result in an absence of REP-1 (Rab escort protein).
Symptoms: The presentation is characterized by progressive vision loss usually in males. The first symptom is often impairment of night vision early in childhood (nyctalopia). Next, the field of vision narrows with a decrease in visual acuity. Ultimately the condition leads to loss of visual acuity and legal blindness as early as the third or fourth decade. However, some studies have shown a majority of patients with choroideremia maintaining good central vision and visual acuity until the seventh decade of life.
Environmental Factors or Other Considerations: Northern Finland has the highest reported prevalence of Choroideremia.
Treatment: The management of choroideremia consists of treating its manifestations: correction of retinal detachment and cataract, UV sunglasses, vitamin supplementation, as well as social support for visual impairment.
Definitive cure does not yet exist, but several trials are underway that use gene therapy to attempt to replace the deficient protein showing promising results. The treatment involves delivery of nonmutated CHM to a patient’s eye in an adenovirus vector. Several trials exhibit promising evidence of vision preservation compared to control.
Pathophysiology: REP-1 (RAB escort protein) is fairly ubiquitous throughout the body. The protein serves an important role in intercellular transport. Most cells in the body have additional sister proteins that can compensate and restore normal cell function in the absence of REP-1 (such as REP-2). However, in the retina REP-2 concentration is diminished or absent resulting in atrophy of cells in the RPE, choroid, and outer retina similar to what is seen in choroideremia.
Differential Diagnosis: Retinitis Pigmentosa, Gyrate atrophy, Ocular albinism.
- Originally published in: Hartnett, Mary Elizabeth. Pediatric retina: medical and surgical approaches. 2nd Philadelphia: Lippincott Williams & Wilkins, 2005.
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Faculty Approval by: M.E. Hartnett, MD
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