Sickle cell disease is a group of disorders that affects hemoglobin, the molecule in red blood cells that delivers oxygen to cells throughout the body. People with this disease have atypical hemoglobin molecules called hemoglobin S, which can distort READ MORE

Silver syndrome belongs to a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by progressive muscle stiffness (spasticity) and, frequently, development of paralysis of the lower limbs (paraplegia). READ MORE

Silver-Russell syndrome is a rare disorder that is characterized by slow growth before and after birth. Babies with this condition typically have a low birth weight and often do not grow and gain weight at the expected rate (failure to thrive). Head READ MORE

Simpson-Golabi-Behmel syndrome is a condition that affects many parts of the body and occurs primarily in males. This condition is classified as an overgrowth syndrome, which means that affected infants are considerably larger than normal at birth (m READ MORE

Sitosterolemia is a condition in which fatty substances (lipids) from vegetable oils, nuts, and other plant-based foods accumulate in the blood and tissues. These lipids are called plant sterols (or phytosterols). Sitosterol is one of several plant s READ MORE

Sjögren syndrome is a disorder whose main features are dry eyes and a dry mouth. The condition typically develops gradually beginning in middle adulthood but can occur at any age. Sjögren syndrome is classified as an autoimmune disorder, one of a lar READ MORE

Sjögren-Larsson syndrome is a condition that affects the skin and eyes as well as the brain and spinal cord (central nervous system). Infants with Sjögren-Larsson syndrome tend to be born prematurely. At birth, the skin may be thicker than normal (hy READ MORE

SLC35A2 -congenital disorder of glycosylation ( SLC35A2 -CDG, formerly known as congenital disorder of glycosylation type IIm) is an inherited condition that causes neurological problems and other abnormalities. This disorder's signs and symptoms and READ MORE

SLC4A1 -associated distal renal tubular acidosis is a kidney (renal) disorder that sometimes includes blood cell abnormalities. The kidneys normally filter fluid and waste products from the body and remove them in urine; however, in people with dista READ MORE

Small fiber neuropathy is a condition characterized by severe pain attacks that typically begin in the feet or hands. As a person ages, the pain attacks can affect other regions. Some people initially experience a more generalized, whole-body pain. T READ MORE

Smith-Kingsmore syndrome is a neurological disorder characterized by a head that is larger than normal (macrocephaly), intellectual disability, and seizures. In some people with this condition, the ability to speak is delayed or never develops. Some READ MORE

Smith-Lemli-Opitz syndrome is a developmental disorder that affects many parts of the body. This condition is characterized by distinctive facial features, small head size (microcephaly), intellectual disability or learning problems, and behavioral p READ MORE