Smith-Lemli-Opitz syndrome

What is Smith-Lemli-Opitz Syndrome?

Smith-Lemli-Opitz syndrome (SLOS) is an inherited condition in which the body's ability to make cholesterol is impaired. It is caused by harmful genetic changes in the DHCR7 gene. Cholesterol is critical for the structure of cells and the development of a baby. It also plays an important role in the production of different hormones and digestive acids. Individuals with SLOS have very low cholesterol levels, which ultimately disrupts growth and development and causes birth defects. The severity and types of symptoms can vary from individual to individual.

In children with little or no ability to make cholesterol, symptoms are severe. Common birth defects include an abnormally small head (microcephaly), an opening in the roof of the mouth (cleft palate), heart defects, and abnormal genitalia in male infants. Affected infants often have difficulty feeding because they lack the sucking reflex and have weak muscle tone (hypotonia). Some individuals have extra fingers or toes, as well as fused second and third toes on both feet (2-3 toe syndactyly). Infants with the severe form of SLOS grow slowly, and most have moderate-to-severe intellectual disability and behavioral issues. Severely affected infants may also have problems with their kidneys, which can be life-threatening. Sensitivity to sunlight (photosensitivity) is common in adults with SLOS.

Some children have a milder form of the condition in which the body can produce some cholesterol. Symptoms may include developmental delays, toe defects, slow growth, and short stature. These children generally learn to walk and talk, although most do not become independent adults.

How common is Smith-Lemli-Opitz Syndrome?

The incidence of SLOS in the population is an estimated 1 in 20,000 to 1 in 60,000 people. The incidence of SLOS is more common among individuals of European ancestry, especially in people from Slovakia and the Czech Republic. SLOS syndrome is rare among people of African and Asian descent.

How is Smith-Lemli-Opitz Syndrome treated?

There is no cure for SLOS. Treatment for the condition is directed at managing the specific symptoms an individual has. This often means receiving care from a team of specialists that may include physicians, dietitians, speech pathologists, occupational therapists, physical therapists, and social workers. The primary treatment for SLOS is to supplement the patient's diet with large amounts of cholesterol, either in the form of purified cholesterol or from high-cholesterol foods (such as egg yolks and cream). Individuals diagnosed with SLOS will often benefit from receiving early intervention and other supportive services beginning at a young age. Some birth defects may be repaired with surgery. Additional symptoms are treated as they arise.

Because the condition can cause extreme sun sensitivity, people with SLOS should try to stay out of the sun for long periods of time. Additional protective measures include wearing sunscreen, sunglasses, and appropriate clothing when outdoors.

What is the prognosis for a person with Smith-Lemli-Opitz Syndrome?

Although serious internal malformations can lead to early death, many people with SLOS can have a normal lifespan with proper nutrition and medical care.