Cri-du-Chat Syndrome

5p minus Society (USA)
International Cri du Chat (5p-)

Fragile X Syndrome

FRAXA Research Foundation (USA)
National Fragile X Foundation (USA)
The Fragile X Research Foundation of Canada

Neurofibromatosis

Neurofibromatosis Network
Children’s Tumor Foundation

PKU

National PKU News

Prader-Willi Syndrome

The Prader-Willi Syndrome Association (PWSA) (USA)
Prader-Willi Alliance of NY (USA)

Rett Syndrome

International Rett Syndrome Association (USA)

Smith-Lemli-Opitz Syndrome

Smith-Lemli-Opitz/RSH Foundation

Smith-Magenis Syndrome

Parents and Researchers interested in Smith-Magenis Syndrome (PRISMS) (USA)

Tuberous Sclerosis

Tuberous Sclerosis Alliance (USA)

Williams Syndrome

Williams Syndrome Association (WSA) (USA)

Other Genetics Websites:

Your Genes, Your Health
Online Mendelian Inheritance in Man
Genetics Education Center, University of Kansas Medical Center
Genetic and Rare Diseases Information Center (GARD)

Genetics Website (In English, French, Spanish, German, Italian & Portuguese!):

Orphanet