What is the definition of Smith-Lemli-Opitz Syndrome?

Smith-Lemli-Opitz syndrome (SLOS) is a rare genetic condition affecting multiple body systems. Signs and symptoms may include characteristic facial features, small head size, growth and developmental delays, and intellectual and behavioral problems. Individuals with SLOS have abnormally low levels of cholesterol in their blood and high levels of a chemical known as 7-dehydrocholestrol. The severity of symptoms varies from individual to individual. Many babies have feeding difficulties and growth issues. Some are born with heart, kidney, and adrenal problems. Most people with SLOS have some degree of intellectual and behavioral difficulties. This condition is caused by genetic changes (DNA variants) in the DHCR7 gene and is inherited in an autosomal recessive pattern. This condition is diagnosed based on the features and laboratory and genetic testing. Treatment is based on the symptoms.

What are the alternative names for Smith-Lemli-Opitz Syndrome?

  • Smith Lemli Opitz syndrome
  • SLO syndrome
  • 7-Dehydrocholesterol reductase deficiency
  • RSH syndrome
  • SLOS
  • Rutledge lethal multiple congenital anomaly syndrome
  • Polydactyly, sex reversal, renal hypoplasia, and unilobular lung
  • Lethal acrodysgenital syndrome

What are the causes for Smith-Lemli-Opitz Syndrome?

Smith-Lemli-Opitz syndrome (SLOS) is caused by genetic changes (DNA variants) in the DHCR7 gene. 

What are the symptoms for Smith-Lemli-Opitz Syndrome?

The following list includes the most common signs and symptoms in people with Smith-Lemli-Opitz syndrome. These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list also does not include every symptom or feature that has been described in this condition. Signs and symptoms of Smith-Lemli-Opitz syndrome may include:
  • Microcephaly
  • Intellectual disability
  • Global developmental delay
  • Distinctive facial features
  • Feeding difficulties
  • Cleft palate
  • Underdeveloped male genitalia
  • Defect in the opening of the penis (hypospadias)
  • Extra fingers and toes (Postaxial polydactyly)
  • Webbed toes (2-3 syndactyly)
  • Heart abnormalities
Newborns with Smith-Lemli-Opitz syndrome (SLOS) are often born with characteristic facial features, extra fingers and toes, and small chin with a cleft palate. Some have heart defects, feeding issues, and gastrointestinal problems. Children with SLOS have some degree of intellectual disability and behavioral issues, such as sleep disturbances. They are often very sensitive to sunlight. Lower levels of cholesterol and increased levels of a chemical known as 7-dehydrocholesterol (7DHC) are associated with more severe features and symptoms.

What are the current treatments for Smith-Lemli-Opitz Syndrome?

There is no specific treatment for Smith-Lemli-Opitz syndrome, and treatment is based on the symptoms. There is some evidence that adding cholesterol to the diet can be helpful, especially if started early in life. Other treatments may include surgery, medications, and therapy for intellectual and developmental issues. Some of the specialists who may be involved in the care of someone with Smith-Lemli-Opitz syndrome include:
  • Genetics specialist
  • Gastroenterologist
  • Neurologist
  • Cardiologist
  • Dietitian or nutritionist

How is Smith-Lemli-Opitz Syndrome diagnosed?

Smith-Lemli-Opitz syndrome is diagnosed based on a clinical exam and a blood test to detect high levels of 7-dehydrocholesterol in the blood. Genetic testing for variants in the DHCR7 gene can confirm the diagnosis.

Is Smith-Lemli-Opitz Syndrome an inherited disorder?

Smith-Lemli-Opitz syndrome is inherited in an autosomal recessive pattern. All individuals inherit two copies of each gene. Autosomal means the gene is found on one of the numbered chromosomes found in both sexes. Recessive means that both copies of the responsible gene must be changed to have the condition.    People with autosomal recessive conditions inherit one changed gene from each of their parents. The parents are known as carriers. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When two carriers of an autosomal recessive condition have children, there is a 25% (1 in 4) chance to have a child with the condition.
  • Journal: Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics
  • Published —
Clinical and genetic analysis of a Chinese pedigree affected with Smith-Lemli-Opitz syndrome.