Smith-Lemli-Opitz syndrome


Type of disease: Rare conditions

Smith-Lemli-Opitz (SLO) syndrome is a genetic disorder that affects a child’s physical and brain (cognitive) development. Infants with SLO syndrome have weak muscles (hypotonia), difficulties with feeding, and slow growth. SLO syndrome can also cause abnormalities (malformations) of the heart, lungs, kidneys, stomach and intestines (GI tract), or genitalia. Other physical features can include fusion between the 2nd and 3rd toes (syndactyly), extra fingers or toes (polydactyly), and a small head (microcephaly). SLO may also cause cognitive issues, including autistic features, learning problems, or behavioral issues.

SLO syndrome is caused by a change (mutation) in a gene called DHCR7. This gene serves as an instruction for the body to make an enzyme, called 7-dehydrocholesterol reductase (7-DHCR), which helps produce a fat-like substance that is important for normal development (cholesterol). When a child has mutations in the DHCR7 gene, they are unable to make enough cholesterol for normal growth and development. SLO syndrome is inherited in an autosomal recessive manner, which means a mutation in both copies of the DHCR7 gene that a child has is needed to cause the condition.

SLO syndrome is suspected when a child has physical features of the condition that are seen on physical exam, along with learning problems or behavioral issues. Diagnosis of the condition is confirmed if a child has a low 7-DHCR enzyme level or if mutations are identified with genetic testing of the DHCR7 gene. There is no cure for this disease. However, providing cholesterol supplement may improve some symptoms. If malformations are severe, surgery may be needed. Therapies can improve development and learning issues. If your child has been diagnosed with SLO syndrome, talk with their doctor to discuss all current treatment recommendations. More information and support are available though support groups.

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