[Identification of the molecular bases of retinal dystrophies: two divergent situations and their implications]

In industrialized countries inherited retinal dystrophies are the leading cause of legal blindness across all ages, together with age-related macular degeneration. Most retinal dystrophies were first described between the end of the 19th century and the beginning of the 20th century as "chorioretinal heredodegenerations". This term is now obsolete, although it has the merit of mentioning the ineluctably degenerative nature of these inherited blinding disorders. These diseases are now known to be highly heterogeneous, both clinically and genetically. However, their molecular bases remained a mystery until the early 1980s, when the advent of genetic engineering offered the possibility of mapping and identifying genes of unknown structure and function. Within a few decades, better knowledge of the molecular bases of retinal dystrophies led to significant medical and genetic advances. Two divergent situations were encountered. First, several phenotypes previously thought to be different clinical entities have been united through the identification of mutations in the same gene. Conversely, some other disorders have turned out to comprise two or more genetically and pathophysiologically distinct entities. This rapid progress in medical knowledge has profoundly modified the relationship between patients and caregivers, sound scientific information being the first form of care for patients with incurable diseases. The genetic deciphering of two diseases, Leber congenital amaurosis and Stargardt disease, represents a good example of how basic knowledge and the patient-carer relationship have evolved in recent decades.