34.1 Features
Pattern dystrophies (PDs) include a group of genetically determined retinal disorders, of which, a major subset have been associated with mutations in the PRPH2 gene, also known as peripherin/RDS. The phenotype of patients with mutations in this gene is extremely heterogeneous and includes macular pattern-like pigmentary changes, atrophic maculopathy, and a clinical picture that resembles classic retinitis pigmentosa.
Gass described pattern dystrophies in five categories based on clinical findings alone. These include adult-onset foveomacular vitelliform dystrophy, butterfly-shaped pattern dystrophy, reticular dystrophy, multifocal pattern dystrophy simulating Stargardt disease/fundus flavimaculatus, and fundus pulverulentus. Typical characteristics of PDs include progressive retinal pigment epithelium (RPE) alterations often accompanied by yellow-dark subretinal material generally involving the macula and posterior pole. Most patients are asymptomatic until their fourth or fifth decade, following which some may experience progressive vision loss due to ensuing chorioretinal atrophy or development of choroidal neovascularization.
PDs have been classified into prominent categories. For more details on adult-onset vitelliform dystrophy, see Chapter 33, Adult Vitelliform Macular Dystrophy. In multifocal pattern dystrophy simulating Stargardt disease/fundus flavimaculatus there is autosomal dominant inheritance of mutations in the peripherin/RDS gene with variable expressivity and reduced penetrance. Butterfly-shaped pattern dystrophy has autosomal dominant mutations in the PRPH2 peripherin/RDS gene. A locus on 5q21.2-q33.2 is also associated with pattern dystrophy. Finally, reticular dystrophy is uncommon with only a few pedigrees reported with possible autosomal dominant or autosomal recessive transmission.
34.1.1 Common Symptoms
Adult Vitelliform Macular Dystrophy
See Chapter 33, Adult Vitelliform Macular Dystrophy.
Multifocal/Fundus Flavimaculatus-Like Dystrophy
Vision is generally good until about the fifth decade, after which vision may remain stable or begin to decline.
Butterfly-Shaped Pattern Dystrophy
Mostly identified on routine ophthalmologic exam; mostly asymptomatic.
Reticular Dystrophy
Usually asymptomatic, vision may be minimally affected in later stages of disease if atrophic changes occur.
34.1.2 Exam Findings
Adult Vitelliform Macular Dystrophy
See Chapter 33, Adult Vitelliform Macular Dystrophy.
Multifocal/Fundus Flavimaculatus-Like Dystrophy
Bilateral, symmetric yellowish pisciform flecks at the level of the RPE are noted throughout the posterior pole, and beyond the vascular arcades (▶ Fig. 34.1). Macular findings may range from various patterns of yellow or gray deposits to well-demarcated chorioretinal atrophy. Clinical findings can be highly variable ranging from minimal findings to a retinitis pigmentosa–like appearance.
Fig. 34.1 Fundus photograph of multifocal pattern dystrophy simulating Stargardt disease/fundus flavimaculatus revealing yellowish pisciform flecks at the level of the retinal pigment epithelium throughout the posterior pole.
Butterfly-Shaped Pattern Dystrophy
Bilateral central accumulation of material at the level of the RPE that appears pigmented or yellow-white, and in the configuration of “arms” or “wings” extending outward in a spoke-like pattern and surrounded by a zone of depigmentation.
Reticular Dystrophy
A meshwork of pigmented spots/lines at the level of the RPE in the macula, described as having a “knotted fishnet” appearance (▶ Fig. 34.2).
Fig. 34.2 (a,b) Butterfly pattern dystrophy demonstrating bilateral central accumulation of material at the level of the retinal pigment epithelium (RPE) that appears pigmented or yellow-white, and in the configuration of “arms” or “wings” extending outward. (c,d) The yellowish-white deposits block fluorescence while areas of RPE loss exhibit window defect and hyperfluorescence without leakage on fluorescein angiography. Genetic testing revealed a mutation in the PRPH2 gene.
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