RESEARCH ARTICLE Leber Congenital Amaurosis: Comprehensive Survey of the Genetic Heterogeneity, Refinement of the Clinical Definition, and Genotype–Phenotype Correlations as a Strategy for Molecular Diagnosis Sylvain Hanein, 1 Isabelle Perrault, 1 Sylvie Gerber, 1 Gae ¨lle Tanguy, 1 Fabienne Barbet, 1 Dominique Ducroq, 1 Patrick Calvas, 2 He ´le `ne Dollfus, 3 Christian Hamel, 4 Tuija Lopponen, 5 Francis Munier, 6 Louisa Santos, 7 Stavit Shalev, 8 Dimitrios Zafeiriou, 9 Jean-Louis Dufier, 10 Arnold Munnich, 1 Jean-Michel Rozet, 1 and Josseline Kaplan 1n 1 Unite ´ de Recherches sur les Handicaps Ge ´ne ´tiques de l’Enfant, Ho ˆpital Necker - Enfants Malades, Paris, France; 2 Service de Ge ´ne ´tique Me ´dicale, Hopital Purpan, Toulouse, France; 3 Clinique Ophtalmologique, Hopitaux Universitaires de Strasbourg, Strasbourg, France; 4 Unite ´ INSERM U-254, Montpellier, France; 5 Clinical Genetics Unit, Turku University Hospital, Turku, Finland; 6 Hopital Ophtalmique Jules Gonin, Lausanne, Switzerland; 7 Servic ¸o de Genetica, Hospital Dona Estefa ˆnia, Lisboa, Portugal; 8 Technion - Israel Institute of Technology, Haifa, Israel; 9 1st Department of Pediatrics, Aristote University, Thessaloniki, Greece; 10 Service d’ophtalmologie, Ho ˆpital Necker, France Communicated by Jean-Claude Kaplan Leber congenital amaurosis (LCA) is the earliest and most severe form of all inherited retinal dystrophies, responsible for congenital blindness. Disease-associated mutations have been hitherto reported in seven genes. These genes are all expressed preferentially in the photoreceptor cells or the retinal pigment epithelium but they are involved in strikingly different physiologic pathways resulting in an unforeseeable physiopathologic variety. This wide genetic and physiologic heterogeneity that could largely increase in the coming years, hinders the molecular diagnosis in LCA patients. The genotyping is, however, required to establish genetically defined subgroups of patients ready for therapy. Here, we report a comprehensive mutational analysis of the all known genes in 179 unrelated LCA patients, including 52 familial and 127 sporadic (27/127 consanguineous) cases. Mutations were identified in 47.5% patients. GUCY2D appeared to account for most LCA cases of our series (21.2%), followed by CRB1 (10%), RPE65 (6.1%), RPGRIP1 (4.5%), AIPL1 (3.4%), TULP1 (1.7%), and CRX (0.6%). The clinical history of all patients with mutations was carefully revisited to search for phenotype variations. Sound genotype–phenotype correlations were found that allowed us to divide patients into two main groups. The first one includes patients whose symptoms fit the traditional definition of LCA, i.e., congenital or very early cone-rod dystrophy, while the second group gathers patients affected with severe yet progressive rod- cone dystrophy. Besides, objective ophthalmologic data allowed us to subdivide each group into two subtypes. Based on these findings, we have drawn decisional flowcharts directing the molecular analysis of LCA genes in a given case. These flowcharts will hopefully lighten the heavy task of genotyping new patients but only if one has access to the most precise clinical history since birth. Hum Mutat 23:306–317, 2004 r 2004 Wiley-Liss, Inc. KEY WORDS: Leber congenital amaurosis; LCA; GUCY2D; retGC1; RPE65; CRX; AIPL1; RPGRIP1; CRB1; TULP1; phenotype–genotype; correlations DATABASE: Multigenic disorder: LCA – OMIM: 204000 INTRODUCTION Originally described by Theodore Leber in 1869, Leber congenital amaurosis (LCA; MIM# 204000) is the earliest and most severe form of all hereditary retinal dystrophies, responsible for congenital blindness [Leber, 1869]. The diagnosis is usually made at birth or during the first months of life in an infant with total blindness or greatly impaired vision, normal fundus, and non-recordable electroretinogram (ERG) [Franceschetti and Dieterle, The Supplementary Material referred to in this article can be found at http://www.mrw.interscience.wiley.com/suppmat/1059-7794/ suppmat/ Received 31 July 2003; accepted revised manuscript 25 November 2003 Grant sponsors: Association Retina France; Association Valentin Haˇy; Foundation Fighting Blindness. Sylvain Hanein and Isabelle Perrault contributed equally to this paper. n Correspondence to: Josseline Kaplan, Unite¤ de Recherches sur les Handicaps Ge¤ ne¤ tiques de l’Enfant. Ho“ pital Necker - Enfants Malades, 149 rue de Se' vres,75743 Paris Cedex 15, France. E-mail: kaplan@necker.fr DOI 10.1002/humu.20010 Published online inWiley InterScience (www.interscience.wiley.com) r r 2004 WILEY-LISS, INC. HUMAN MUTATION 23:306^317 (2004)