Clinical characteristics: Choroideremia (CHM) is characterized by progressive chorioretinal degeneration in affected males and milder signs in carrier females. Typically, symptoms in affected males evolve from night blindness to peripheral visual field loss, with central vision preserved until late in life. Although carrier females are generally asymptomatic, signs of chorioretinal degeneration can be observed with careful fundus examination. These signs become more readily apparent after the second decade.
Diagnosis/testing: The diagnosis of CHM can be made clinically, based on the fundus examination and family history consistent with X-linked inheritance. The diagnosis is confirmed with the identification of a pathogenic variant in CHM which encodes the protein REP-1.
Management: Treatment of manifestations: Surgical correction of retinal detachment and cataract as needed; UV-blocking sunglasses for outdoors; appropriate dietary intake of fresh fruit, leafy green vegetables; antioxidant vitamin supplement as needed; regular intake of dietary omega-3 very-long-chain fatty acids, including docosahexaenoic acid; low vision services as needed; counseling as needed to help cope with depression, loss of independence, fitness for driving, and anxiety over job loss. Surveillance: Periodic ophthalmologic examination and Goldmann visual field examinations to monitor progression. Agents/circumstances to avoid: UV exposure from sunlight reflected from water and snow.
Genetic counseling: CHM is inherited in an X-linked manner. An affected male transmits the pathogenic variant to all of his female offspring and none of his male offspring. A carrier female has a 50% chance of passing the pathogenic variant to her offspring: males who inherit the pathogenic variant will be affected; females who inherit the pathogenic variant will be carriers and will usually not be affected. Carrier testing for at-risk female relatives and prenatal diagnosis for pregnancies at increased risk are possible if the pathogenic variant has been identified in an affected family member.
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