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Purpose : To describe clinical phenotype in patients of northern Sweden affected by recessive retinitis pigmentosa (ARRP) caused by mutations in Eyes Shut Homolog (Drosophila) (EYS) gene.

Methods : Whole exome sequencing (WES) and multiple ligation dependent prode amplification (MLPA) were used for identification of EYS sequence variants in a cohort of ARRP patients (n=148) from northern Sweden. The patients with EYS mutations were ophthalmologically examined over time using visual acuity (ETDRS), visual fields, slit lamp and fundus examination and ocular coherence tomography (OCT). Dark adaptometry and full-field electroretionograms (ERG) was performed.

Results : Phenotype characterization was done in 13 ARRP cases with EYS mutations representing five bi-allelic sequence variants, three of which were novel. Only one variant was detected in two cases. The phenotypic outcome was predominately presented as classical RP aggravating in young adulthood. However, among these patients we observed a variation of phenotypic expression with initial paracentral to central macular affection of the retina and areolar retinal degeneration with electrophysiological outcome of only slightly subnormal responses of both rods and cones in late adulthood (60 y/o), clinically defined as areolar atrophy.

Conclusions : The EYS mutations account for 10% of ARRP in northern Sweden. The phenotype presents both typical classical RP and chorioretinal degenerative retinal disease, areolar dystrophy. This suggests that molecular genetic testing of the EYS is crucial when both RP and pattern macular diseases are clinically diagnosed.