Inherited retinal dystrophies, such as retinitis pigmentosa (RP), include a group of relatively rare hereditary diseases caused by mutations in genes that code for proteins involved in the maintenance and function of the photoreceptor cells (cones and rods). The different forms of RP consist of progressive neurodegenerative disorders which are generally related to various and severe limitations of visual performances. In the course of typical RP (rod-cone dystrophy), the affected individuals first experience night-blindness and/or visual field constriction (secondary to rod dysfunctions), followed by variable alterations of the central vision (due to cone damages). On the other hand, during the atypical form of RP (cone-rod dystrophy), the cone’s functionalities are prevalently disrupted in comparison with the rod’s ones. The basic diagnosis of RP relies upon the documentation of unremitting loss in photoreceptor activity by electroretinogram and/or visual field testing. The prevalence of all RP typologies is variably reported in about one case for each 3000-5000 individuals, with a total of about two millions of affected persons worldwide. The inherited retinal dystrophies are sometimes the epiphenomenon of a complex framework (syndromic RP), but more often they represent an isolated disorder (about 85-90 % of cases). Although 200 causative RP mutations have been hitherto detected in more than 100 different genes, the molecular defect is identifiable in just about the 50% of the analyzed patients with RP. Not only the RP genotypes are very heterogeneous, but also the patients with the same mutation can be affected by different phenotypic manifestations. RP can be inherited as autosomal dominant, autosomal recessive or X-linked trait, and many sporadic forms are diagnosed in patients with no affected relatives. Dissecting the clinico-genetic complexity of RP has become an attainable objective by means of large-scale research projects, in which the collaboration between ophthalmologists, geneticists, and epidemiologists becomes a crucial aspect. In the present review, the main issues regarding clinical phenotyping and epidemiologic criticisms of RP are focused, especially highlighting the importance of both standardization of the diagnostic protocols and appropriateness of the disease’s registration systems.

Purpose To report the clinical association between macular coloboma (early-onset macular dystrophies/atrophic changes) and different phenotypes of retinitis pigmentosa (RP). Methods Three young-adult siblings, two males and one female, were retrospectively studied. These patients underwent two complete ophthalmologic examinations (27-month follow-up), including orthoptic evaluation, colour vision test, visual field, corneal topography, electronystagmography, fluorescein angiography, and electroretinography. Eye check, automated visual field test, and complete electroretinographic study were also conducted on other asymptomatic members of the same family. Results All symptomatic siblings were affected by manifest congenital nystagmus, poor visual acuity, and progressive visual field impairment in both eyes, bilaterally presenting macular coloboma associated with three different RP patterns: classic RP; mild dystrophy of the retinal pigment epithelium, associated with subnormal electroretinographic findings (subclinical form of RP); and sector RP. The ophthalmologic reports regarding their deceased father documented that he had suffered from the same alterations of ocular movements and visual performances diagnosing, in both eyes, extensive atrophic changes of the macular area completely surrounded by pigmented bone spicules (RP-type tapeto-retinal dystrophy). The other investigated relatives did not show any specific and/or significant ocular disorder. Conclusions In these three adult members of the same family, the concomitance between macular coloboma and different intrafamilial RP phenotypes is described. This association represents an autosomal dominant clinical entity, hitherto observed only in non familial sporadic cases.