Page 13 - Demo

General introduction111IntroductionImproved medical care for people with an intellectual disability in combination with advances in clinical genetic testing have resulted in an increased number of adults known to have a genetic neurodevelopmental disorder (GND). In the past, most studies focused on children with a GND, leaving a knowledge gap regarding conditions that are present at adult age.1The studies described in this thesis were conducted to characterize GNDs, with a focus on 22q11.2 deletion syndrome (22q11.2DS), at adult age. Study topics included parkinsonism and Parkinson’s disease, otolaryngology, ophthalmology, and trauma-related disorders. In addition, the retina was examined for potential biomarkers for age-related disorders in 22q11.2DS. The following paragraphs will give an introduction to the study topics included in this thesis.Genetic neurodevelopmental disordersIn the absence of one generally accepted definition, the following criteria for a GND were used, in line with the definition for “neurodevelopmental abnormality” developed by the Human Phenotype Ontology (https://hpo.jax.org/); 1) a deviation from the normal of the neurological development of a child, including any or all aspects of the development of personal, social, motor, and cognitive abilities, 2) in the presence of a disease-causing genetic variant.A well-known example of a GND is Down syndrome, that has an estimated prevalence of 1:794 live births.2 Rare GNDs, meaning less than 2000 individuals in the general population are affected,3 include for example 22q11.2DS and Rett syndrome. 4, 5 Although individually rare, the prevalence of these GNDs as a group is about 3% of the population.6 Most GNDs are associated with intellectual disabilities,7 which is characterized by significant limitations in cognitive and adaptive skills.8 Therefore, and because of limited studies in GNDs, prevalence rates and characteristics of conditions in adults with 22q11.2DS in this thesis are often compared to results of adults with an intellectual disability, in addition to adults from the general population.