Table 2.

Web resources for constitutional ring chromosomes

Organization	Link
All ring chromosomes
A Human Ring Chromosome Registry	http://yybio.tech/hrc/
Small supernumerary marker chromosomes	http://cs-tl.de/DB/CA/sSMC/0-Start.html
UNIQUE	https://rarechromo.org/here e.g. patient information sheets for RC 9, RC 12, RC 14, R 18, RC 22
Chromosome Disorder Outreach (CDO)	https://chromodisorder.org/
Orphanet	https://www.orpha.net provides basic information on several ring chromosomes
NORD	https://rarediseases.org provides basic information on several ring chromosomes
Ring chromosome 14
Ring 14 International	http://www.ring14.org/eng/
Ring14 Clinical Database	http://www.ring14.org/questionario/crm/
Biobank collection of Ring14 biosamples	Telethon Network of Genetic Biobanks (http://www.ring14.org/eng/341/biobanking-project/)
Ring chromosome 18
Chromosome 18 Registry & Research Society	http://www.chromosome18.org
Facebook group for Ring 18 in Italian	www.facebook.com/groups/325784750908122
Ring chromosome 20
Ring 20 Research and Support UK	https://ring20researchsupport.co.uk/
Ring chromosome 22
Chromosome 22 Central	http://www.c22c.org
Facebook group for Ring 22	https://www.facebook.com/pages/Ring-Chromosome-22/118205524927128
Yahoo group for Ring 22	https://groups.yahoo.com/neo/groups/ring22/info