Atrophy

BASICS


DESCRIPTION


Gyrate atrophy is an autosomal recessive chorioretinal dystrophy that initially presents with nyctalopia and decreased peripheral vision during the first decade of life with progressive constriction of the visual field and eventual loss of central vision.


EPIDEMIOLOGY


Incidence


• Rare disease


• Most commonly reported in Finland with an incidence of approximately 1 in 50,000.


• Generally, presents in the first decade of life


RISK FACTORS


Has been diagnosed in several countries with the largest number of patients reported in Finland (1)[A].


Genetics


• Autosomal recessive inheritance


• Linked to chromosome 10q26, with more than 60 reported mutations


PATHOPHYSIOLOGY


• Patients have a deficiency of ornithine aminotransferase (OAT), which leads to a 10- to 20-fold increase in plasma ornithine levels.


• It is proposed that high ornithine levels may be toxic to the retinal pigment epithelium (RPE).


ETIOLOGY


Enzyme deficiency of OAT.


COMMONLY ASSOCIATED CONDITIONS


• EEG abnormalities and hair abnormalities have been reported in patients with gyrate atrophy.


• Skeletal muscle changes have been reported on CT and MRI.


• White matter lesions and atrophy have been noted on brain MRIs.


DIAGNOSIS


HISTORY


• In the first decade of life, patients typically present with nyctalopia, decreased peripheral vision, myopia, and astigmatism.


• In the second decade of life, patients develop posterior subcapsular cataracts.


• Patients develop progressive constriction of their visual fields with advancing age.


• Patients report a gradual decline in vision with loss of central visual acuity by the fifth decade.


PHYSICAL EXAM


• All patients with gyrate atrophy are myopic, generally with refractive errors−4.00 to −20.00D. Many patients have astigmatism as well.


• By adolescence, posterior subcapsular cataracts are evident.


• Dilated fundus exam initially shows multiple round well-circumscribed areas of chorioretinal atrophy in the periphery and midperiphery of both eyes, generally in a symmetric pattern.


• These areas coalesce with age and move towards the posterior pole, eventually involving the entire fundus.


• Typically, there is a scalloped border between the remaining normal retina and the atrophic retina.


DIAGNOSTIC TESTS & INTERPRETATION


Lab


Plasma ornithine levels should be checked and are generally 10 to 20 times higher than the general population.


Imaging


• Fluorescein angiography typically shows hyperfluorescence of the atrophic areas with possible leakage at the margins between normal and atrophic tissue.


– Optical coherence tomography may demonstrate cystoid macular edema or an epiretinal membrane.


Diagnostic Procedures/Other


Early electroretinographic (ERG) testing shows reduced scotopic and photopic responses. By adulthood, ERG responses are nondetectable.


DIFFERENTIAL DIAGNOSIS


Advanced choroideremia—This is an X-linked recessive disorder with atrophy of the RPE and choriocapillaris.


TREATMENT


MEDICATION


First Line


• Studies have suggested that long-term compliance with a low-protein, low-arginine diet can slow the progression of chorioretinal degeneration (2)[A]. However, even with good compliance, there is still a progressive decline in retinal function. One study of sibling pairs showed that younger siblings with earlier commencement of arginine-restriction had slower progression compared with older siblings with later commencement of dietary modification (3)[A].


• Supplementation with vitamin B6 (pyridoxine) has also been suggested, with additional dietary protein restriction based on ornithine levels. However, the majority of patients with gyrate atrophy are not pyridoxine responders. The dose of pyridoxine supplementation is not well established.


Second Line


Consider cataract extraction when the posterior subcapsular cataracts become visually significant. Patients should be educated that the postoperative visual potential is limited by their retinal disease.


ONGOING CARE


FOLLOW-UP RECOMMENDATIONS


• Gyrate atrophy is a chronic progressive disorder with progressive loss of visual acuity and peripheral vision.


• Patients should be followed routinely for cataract and retinal evaluation.


DIET


See Treatment section.


PATIENT EDUCATION


Consider genetic counseling.


PROGNOSIS


Long-term visual prognosis is poor.



REFERENCES


1. Potter MJ, Berson EL. Diagnosis and treatment of gyrate atrophy. Int Ophthalmol Clin 1993;33:229–236.


2. Kaiser-Kupfer ML, Caruso RC, Valle D, Reed GF. Use of an arginine-restricted diet to slow progressionof visual loss in patients with gyrate atrophy. Arch Ophthalmol 2004;122:982–984.


3. Kaiser-Kupfer ML, Caruso RC, Valle D. Gyrate atrophy of the choroid and retina. Arch Ophthalmol 2002;120:146–153.


4. Takki KK, Milton RC. The natural history of gyrate atrophy of the choroid and retina. Ophthalmology 1981;88:292–301.

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Nov 9, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Atrophy
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