The Short Bowel Syndrome Foundation is a community resource for individuals living with or caring for someone with Short Bowel Syndrome, providing information on the condition, its symptoms, treatments, and various resources to improve quality of life.

The Shwachman-Diamond Syndrome Alliance is a patient advocacy nonprofit focused on accelerating research and therapy development for Shwachman-Diamond Syndrome, bringing together patients, families, doctors, and researchers.

Sick Cells is dedicated to elevating the voices of the sickle cell community, providing education, advocacy, and support to influence policy and improve access to treatments.

The Sickle Cell Association of Texas Marc Thomas Foundation provides support and resources for individuals and families affected by sickle cell disease, focusing on holistic care and community education.

SCDAA is the premier organization advocating for people with sickle cell disease.

The Sickle Cell Disease Foundation is a non-profit organization that supports individuals with sickle cell disease and their families through education, counseling, and various community programs.

The Siegel Rare Neuroimmune Association (SRNA) advocates for individuals with rare neuroimmune disorders such as ADEM, AFM, MOGAD, NMOSD, ON, and TM, providing education, research, and community support programs.

Simons Searchlight is dedicated to creating scientific breakthroughs for rare genetic neurodevelopmental disorders by building a natural history database and resource network, encouraging family participation in research.

Sisters Network® Inc. is a national organization dedicated to raising awareness about breast cancer in the African American community and providing support and education to Black women regarding breast health.

Sisters' Hope Foundation provides support, resources, and advocacy for those impacted by an ALSP diagnosis, aiming to improve their quality of life and build community.

The Skin Cancer Foundation is a nonprofit organization dedicated to educating the public and medical community about skin cancer prevention, early detection, and treatment.

The Skraban-Deardorff Syndrome Foundation supports individuals affected by Skraban-Deardorff Syndrome through research funding and community engagement.

SkyHope provides free medical flights for patients and veterans who need to access medical care that is too far to reach by car.

The Smith-Kingsmore Syndrome Foundation is dedicated to improving the lives of individuals affected by Smith-Kingsmore syndrome through research and community support.

The Smith-Lemli-Opitz Foundation is a nonprofit organization dedicated to improving the quality of life for individuals affected by Smith-Lemli-Opitz syndrome through education, support for families, and raising awareness about the condition.

The SMS Foundation UK is a charity that supports families living with Smith-Magenis syndrome (SMS) by providing emotional support, practical guidance, and resources for parents, carers, and professionals.

The Smith-Magenis Syndrome Research Foundation supports research to improve the understanding and treatment options for individuals affected by Smith-Magenis Syndrome.

The Snow Foundation is dedicated to supporting patients with Wolfram syndrome by advocating for research towards a cure and providing resources to improve their quality of life.

The Snyder-Robinson Foundation is dedicated to advancing research and support for individuals affected by Snyder-Robinson Syndrome and related disorders, aiming to improve their lives through medical advancements and community connection.

The Society for Investigative Dermatology (SID) is a not-for-profit organization dedicated to advancing the sciences relevant to skin disease through education, advocacy, and scholarly exchange of scientific information.