SUCLA2-related mitochondrial DNA (mtDNA) depletion syndrome is an inherited disorder that affects the early development of the brain. Affected infants typically develop weak muscle tone (hypotonia) in the first few months of life. In these infants, h READ MORE

SUCLG1-related mitochondrial DNA (mtDNA) depletion syndrome is an inherited disorder that affects the early development of the brain. Signs and symptoms typically appear soon after birth. Most affected children develop severe brain dysfunction and mu READ MORE

Sudden infant death with dysgenesis of the testes syndrome (SIDDT) is a rare condition that is fatal in the first year of life; its major features include abnormalities of the reproductive system in males, feeding difficulties, and breathing problems READ MORE

Supravalvular aortic stenosis (SVAS) is a heart defect that develops before birth. This defect is a narrowing (stenosis) of the large blood vessel that carries blood from the heart to the rest of the body (the aorta). The condition is described as su READ MORE

Surfactant dysfunction is a lung disorder that causes breathing problems. This condition results from abnormalities in the composition or function of surfactant, a mixture of certain fats (called phospholipids) and proteins that lines the lung tissue READ MORE

Swyer syndrome is a condition that affects sex development. Sex development usually follows a particular path based on an individual's chromosomes; however, in Swyer syndrome, sex development is not typical for the affected individual's chromosomal p READ MORE

SYNGAP1 -related intellectual disability is a neurological disorder characterized by moderate to severe intellectual disability that is evident in early childhood. The earliest features are typically delayed development of speech and motor skills, su READ MORE

Systemic lupus erythematosus (SLE) is a chronic disease that causes inflammation in connective tissues, such as cartilage and the lining of blood vessels, which provide strength and flexibility to structures throughout the body. The signs and symptom READ MORE

Systemic mastocytosis is a blood disorder that can affect many different body systems. Individuals with the condition can develop signs and symptoms at any age, but it usually appears after adolescence. Signs and symptoms of systemic mastocytosis oft READ MORE

Systemic scleroderma is an autoimmune disorder that affects the skin and internal organs. Autoimmune disorders occur when the immune system malfunctions and attacks the body's own tissues and organs. The word "scleroderma" means hard skin in Greek, a READ MORE

T-cell immunodeficiency, congenital alopecia, and nail dystrophy is a type of severe combined immunodeficiency (SCID), which is a group of disorders characterized by an almost total lack of immune protection from foreign invaders such as bacteria and READ MORE

Tangier disease is an inherited disorder characterized by significantly reduced levels of high-density lipoprotein (HDL) in the blood. HDL transports cholesterol and certain fats called phospholipids from the body's tissues to the liver, where they a READ MORE