Sylvia is a clinical supervisor of the specialist training program at Prinsenstichting and a teacher at the Erasmus University Medical Centre, Rotterdam. She did a PhD on Self-injurious Behaviour in Cornelia de Lange syndrome. 

She works at Prinsenstichting, at the Amsterdam Expertise Centre for Neurodevelopmental Disorders (including Cornelia de Lange syndrome) at the Amsterdam University Medical Centre, and at the Centre for Consultancy and Expertise (CCE). 

She is a Physician for Individuals with Intellectual Disabilities (AVG). She received her specialist training at the Prinsenstichting and at the Erasmus University Medical Centre, Rotterdam. 

First trained as a paediatrician before specializing in medical genetics in Zürich and Geneva. Since his beginnings in this field, he always has had a special interest for rare disorders and the delineation of syndromes. From 1992 until 2018 he worked in the Service of Genetic Medicine at the Geneva University Hospitals, where his main activity was seeing children and adults with unclear conditions in order to try and find the cause of their problems. Since his part-retirement, he is now in charge of the consultations in the Service of Genetics of his hometown hospital. 

He is father of Rai (CdLS, November 1999). Motivated to know all you need to know about CdLS he joined the dutch 'vereniging Cornelia de Lange syndroom' and became chairman of this group in 2008. In Buenos Aires at the world conference about CdLS in Argentina he was elected chairman of the CdLS World federation. 

Gerritjan is an Information Architect. Within the CdLS World federation executive council he is especially advocating the role of family members and the CdLS Patients so they are involved in Knowledge Development and sharing their experience with other family members, professionals or researchers.