See Rare Diseases by First Letter (S)
- Sacrococcygeal Teratoma
- Sandhoff Disease
- SAPHO Syndrome
- Sarcoidosis
- Scheuermann Disease
- Schistosomiasis
- Schwannoma
- Scleroatonic Muscular Dystrophy
- Scott Syndrome
- Scurvy
- Selective IgA Deficiency
- Semantic Dementia
- Seminoma
- Senior Loken Syndrome
- Sensory Neuropathy Type 1
- Septo-optic Dysplasia
- Serpiginous Choroiditis
- Sertoli-leydig Cell Tumors
- Severe Acute Respiratory Syndrome
- Severe Combined Immunodeficiency
- Sezary Syndrome
- Sharp Syndrome
- Shigellosis
- Short Bowel Syndrome
- Shprintzen-Goldberg Craniosynostosis Syndrome
- Shwachman-Diamond Syndrome
- Sialadenitis
- Sickle Cell Anemia
- Sideroblastic Anemia Pyridoxine-refractory Autosomal Recessive
- Siderosis
- Silicosis
- Single Ventricular Heart
- Sinonasal Undifferentiated Carcinoma
- Sitosterolemia
- Situs Inversus
- Small Intestine Cancer
- Small Non-cleaved Cell Lymphoma
- Smallpox
- Smith-Magenis Syndrome
- Soft Tissue Sarcoma
- Somatostatinoma
- Spasmodic Dysphonia
- Spastic Paraparesis
- Spastic Paraplegia Epilepsy Mental Retardation
- Spheroid Body Myopathy
- Sphingolipidosis
- Spielmeyer-Vogt Disease
- Spina Bifida
- Spinal Cord Neoplasm
- Spinal Muscular Atrophy
- Spinal Muscular Atrophy 1
- Spinal Muscular Atrophy Type 2
- Spinal Shock
- Spinocerebellar Ataxia
- Spinocerebellar Ataxia 1
- Spinocerebellar Ataxia 10
- Spinocerebellar Ataxia 2
- Spinocerebellar Ataxia 3
- Spinocerebellar Ataxia Type 6
- Splenomegaly
- Spondylarthropathy
- Spontaneous Coronary Artery Dissection
- Sporotrichosis
- Squamous Cell Carcinoma of the Head and Neck
- Stargardt Disease
- Status Epilepticus
- Stevens-Johnson Syndrome
- Stickler Syndrome
- Stiff Person Syndrome
- Still's Disease Adult Onset
- Stomach Carcinoma
- Streptococcal Group A Invasive Disease
- Stress Cardiomyopathy
- Strongyloidiasis
- Sturge-Weber Syndrome
- Subcutaneous Panniculitis-like T-cell Lymphoma
- Subependymal Giant Cell Astrocytoma
- Subependymoma
- Succinic Semialdehyde Dehydrogenase Deficiency
- Sudden Infant Death Syndrome
- Sulfite Oxidase Deficiency
- Superficial Spreading Melanoma
- Superior Limbic Keratoconjunctivitis
- Superior Vena Cava Syndrome
- Supraglottic Laryngeal Cancer
- Supratentorial Primitive Neuroectodermal Tumor
- Supratentorial Primitive Neuroectodermal Tumors, Childhood
- Supravalvular Aortic Stenosis
- Susac Syndrome
- Sydenham's Chorea
- Synovial Sarcoma
- Synovitis
- Syringomyelia
- Systemic Candidiasis
- Systemic Capillary Leak Syndrome
- Systemic Mastocytosis
- Systemic Onset Juvenile Idiopathic Arthritis