Page 13 - Characterization of genetic neurodevelopmental disorders at adult age, with a focus on 22q11.2 deletion syndrome - Emma Boersma

General introduction
Introduction
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Improved 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.1
The 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 disorders
In 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.
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