Smith-Lemli-Opitz syndrome

What is Smith-Lemli-Opitz Syndrome?

Smith-Lemli-Opitz syndrome, or SLO syndrome, is an inherited disorder in which the body's ability to make cholesterol is impaired due to a deficient enzyme. Cholesterol is critical for the structure of cells, and is necessary for normal fetal development. It also plays an important role in the production of hormones and digestive acids. In addition to low cholesterol levels, SLO syndrome also causes toxic byproducts of cholesterol production to build up throughout the body, further disrupting growth and development.

In children with little or no ability to make cholesterol, symptoms are severe. These infants are commonly born with an abnormally small head, cleft palate, and weak muscle tone. They often have difficulty feeding because they lack the sucking reflex or have an abnormally small stomach that causes persistent vomiting. Some have extra fingers or toes as well as the typical fused second and third toes on both feet. Male infants may have deformed or underdeveloped genitalia.

Infants with the severe form of SLO syndrome grow slowly and 90% have moderate to severe mental disability. Severely affected infants may also have heart defects and problems with their kidneys, causing death in the first months of life.

Some children are born with a milder form of the condition in which the body can produce some cholesterol. Symptoms may include developmental delays, feet with the second and third toes fused together, slow growth, and short stature. These children generally learn to walk and talk and can acquire other skills, although they can rarely live independently as adults. Adults with the disease often show aggressive behavior.

Symptoms of the disease can vary from person to person. Some affected people have only minor symptoms of the condition.

How common is Smith-Lemli-Opitz Syndrome?

Smith-Lemli-Opitz syndrome affects an estimated 1 in 20,000 to 60,000 people. This disease is more common in those of European ancestry, particularly those in Slovakia and the Czech Republic. It is very rare among people of African and Asian descent.

How is Smith-Lemli-Opitz Syndrome treated?

There is no cure for SLO syndrome, but its symptoms can be addressed. The primary treatment is to supplement the person's diet with large amounts of dietary cholesterol, either in the form of purified cholesterol or in foods such as egg yolks and cream. This has been shown to improve symptoms. Early intervention and therapy helps with speech and physical disabilities. Medication may treat symptoms such as vomiting, constipation, and gastroesophageal reflux. Surgery and orthotics can help muscle spasms and improve mobility.

Because the condition can cause extreme sun sensitivity, people with SLO syndrome should always wear sunblock, sunglasses, and appropriate clothing when they go outdoors.

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

Although serious internal malformations can lead to early death, with good nutrition and medical care many people with SLO syndrome can have a normal lifespan. Mental disability typically prevents people with this disease from living independently.