Genetically isolated populations Implications for genetic care

Genetically isolated populations exist worldwide. They provide unique opportunities for genetic studies that may eventually lead to useful clinical applications. This thesis concerns such genetic studies in a young genetically isolated population in the Netherlands.
We identified the genetic causes of two autosomal recessive disorders (fetal akinesia deformation sequence and XX female gonadal dysgenesis) and studied the phenotypic variation of another autosomal recessive disorder (retinitis pigmentosa type 12).
Furthermore, we implemented a preconception outpatient clinic offering carrier screening for multiple severe recessive disorders in this population. Approximately one-third of the individuals visiting the clinic turned out to be a carrier of at least one of the disorders and 1 in 25 couples were a carrier couple with a 1-in-4 risk of affected offspring.
We evaluated the carrier screening offer by taking questionnaires and conducting interviews. Attendees were highly familiar with the disorders, demonstrated no major psychological outcomes, experienced no stigmatization, and were very satisfied after testing. All identified carrier couples made reproductive decisions based on their test results.
Although genetically isolated populations may differ in various aspects from other populations and not all research findings may be representative for an outbred population, investigations in isolated populations are helpful in understanding causes of genetic disorders and provide important lessons for further successful and responsible implementation of preconception (expanded) carrier screening and other genetic services in the general population.