Diagnostic Quiz AnswerJanuary 2004
The patients fundus findings along with normal visual acuity suggest a diagnosis of pattern dystrophy.
Pattern dystrophies are usually inherited autosomal dominant disorders that appear during the second to fifth decade of life. They occur bilaterally and are characterized by little to mild decrease in central vision (20/20-20/50) and yellow, orange or gray intraretinal pigmentary deposits in the macular area; the deposits are at the level of the retinal pigment epithelium. Patients are typically asymptomatic.
Differential diagnoses include but are not limited to the following: age-related macular degeneration, fundus flavimaculatus, birdshot retinochoroidapathy, multiple evanescent white-dot syndrome (MEWDS), acute posterior multifocal placoid pigmentary epitheliopathy (APMPPE), autosomal dominant drusen and hypertensive retinopathy.
We subdivide pattern dystrophies into at least five groups according to their pattern of pigmentary distribution. These include Sjogrens reticular dystrophy, butterfly pattern dystrophy, macroreticular dystrophy, fundus pulverulentis and grouped pigmentary dystrophy. All are inherited in an autosomal dominant pattern except for Sjgren"s reticular dystrophy, which is an autosomal recessive trait. Some patients macular patterns demonstrate a combination of all five groups.
Additional diagnostic tests might include:
Pedigree analysis, to trace a possible pattern of inheritance
Electro-oculogram (EOG), which measures the electric potential of the eye. EOG results may vary from normal to subnormal depending on the level of RPE dysfunction.
Fluorescein angiography, which classically demonstrates areas of hypo- and hyperfluorescence that correlate to increased retinal pigmentation and RPE atrophy, respectively. Fluorescein angiography is useful and necessary for detecting choroidal neovascularization, which occurs infrequently.
Pattern dystrophy occasionally occurs secondary to systemic disease. Some 10-20% of patients with pseudoxanthoma elasticum have demonstrated macular pigmentary changes consistent with a pattern dystrophy.1Pattern dystrophies also have been documented in patients with myotonic dystrophy. (For more on these conditions, see The Bowel, the Bones and the Eye, March 2003.)
The visual prognosis is favorable for all pattern dystrophy sub groups. Treatment should include genetic counseling, photodocumentation and laser intervention if choroidal neovascularization is detected. If no CNV is present, annual monitoring with dilated fundus examination is recommended.
Gass JD. Autosomal dominant pattern dystrophies of the retinal pigment epithelium. In: Gass JD. Stereoscopic Atlas of Macular Diseases. Diagnosis and Treatment. Vol 1. 4th ed. St. Louis: Mosby, 1997:314-25.
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