Using a sample of 710,815 liveborn infants throughout Spain, monitored from April, 1976, to December, 1988, by the Spanish Collaborative Study of Congenital Malformations (ECEMC), we estimated the prevalence of each recognized autosomal dominant malformation syndrome for a total prevalence figure of 12.1 per 100,000 live births, including all detected autosomal dominant malformations syndromes. We estimated that the mutation rate for those syndromes was 48.5 per 1,000,000 gametes. The geographical distribution of these syndromes was homogeneous in the Spanish Regions.

From April, 1976, to December, 1988, the Spanish Collaborative Study of Congenital Malformations (ECEMC) monitored a total population of 710,815 liveborn infants in 16 of 17 Spanish Regions and identified 14,439 (2.0%) with congenital defects. Among the malformed children, we identified 73 with well recognized autosomal recessive syndromes, for an overall prevalence rate of 10.3 per 100,000 livebirths and a total carrier frequency of 1/49. Considering the Spanish Regions (Comunidades Autónomas), we analyzed the geographical distributions of these syndromes that were homogeneous. We studied the place of birth of the grandparents to determine the distribution of the gene as well as the gene flow.

Strabismus, or misalignment of the eyes, is the most common ocular disorder in the pediatric population, affecting approximately 2%–4% of children. Strabismus leads to the disruption of binocular vision, amblyopia, social and occupational discrimination, and decreased quality of life. Although it has been recognized since ancient times that strabismus runs in families, its inheritance patterns are complex, and its precise genetic mechanisms have not yet been defined. Family, population, and twin studies all support a role of genetics in the development of strabismus. There are multiple forms of strabismus, and it is not known if they have shared genetic mechanisms or are distinct genetic disorders, which complicates studies of strabismus. Studies assuming that strabismus is a Mendelian disorder have found areas of linkage and candidate genes in particular families, but no definitive causal genes. Genome-wide association studies searching for common variation that contributes to strabismus risk have identified two risk loci and three copy number variants in white populations. Causative genes have been identified in congenital cranial dysinnervation disorders, syndromes in which eye movement is limited or paralyzed. The causative genes lead to either improper differentiation of cranial motor neurons or abnormal axon guidance. This article reviews the evidence for a genetic contribution to strabismus and the recent advances that have been made in the genetics of comitant strabismus, the most common form of strabismus.