Overview
Smith-Lemli-Opitz syndrome (SLOS), also known as 7-dehydrocholesterol reductase deficiency or RSH syndrome, is an inborn error of cholesterol biosynthesis caused by mutations in the DHCR7 gene. This gene encodes the enzyme 7-dehydrocholesterol reductase, which catalyzes the final step in cholesterol synthesis. Deficiency of this enzyme leads to accumulation of 7-dehydrocholesterol (7-DHC) and reduced levels of cholesterol in the blood and tissues, disrupting normal embryonic and postnatal development. SLOS affects multiple body systems and presents with a wide clinical spectrum ranging from mild to severe. Key features include distinctive facial characteristics (microcephaly, ptosis, small upturned nose, micrognathia), intellectual disability of variable degree, behavioral abnormalities (including features of autism spectrum disorder), growth restriction, and limb anomalies — most characteristically syndactyly of the second and third toes. Congenital malformations may involve the heart, kidneys, brain, ganitalia (particularly ambiguous genitalia or hypospadias in males), and gastrointestinal tract (including pyloric stenosis and Hirschsprung disease). Cleft palate and photosensitivity are also commonly observed. Severely affected individuals may have holoprosencephaly and may not survive the neonatal period. There is no cure for SLOS. The primary treatment approach involves dietary cholesterol supplementation, which can improve growth, behavior, and overall well-being in some patients, although it does not reverse structural malformations or significantly cross the blood-brain barrier. Simvastatin has been investigated as an adjunctive therapy to reduce toxic 7-DHC levels, but evidence for its efficacy remains limited. Management is otherwise supportive and multidisciplinary, addressing feeding difficulties, developmental delays, surgical correction of congenital anomalies, and behavioral interventions. Diagnosis is confirmed by elevated 7-DHC levels in plasma and/or molecular testing of the DHCR7 gene.
Clinical phenotype terms— hover any for plain English:
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Neonatal
Begins at or shortly after birth (first 4 weeks)
FDA & Trial Timeline
1 eventUniversity of Colorado, Denver — PHASE2
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Smith-Lemli-Opitz syndrome.
1 clinical trialare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →Rare Disease Specialist
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Smith-Lemli-Opitz syndrome.
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Common questions about Smith-Lemli-Opitz syndrome
What is Smith-Lemli-Opitz syndrome?
Smith-Lemli-Opitz syndrome (SLOS), also known as 7-dehydrocholesterol reductase deficiency or RSH syndrome, is an inborn error of cholesterol biosynthesis caused by mutations in the DHCR7 gene. This gene encodes the enzyme 7-dehydrocholesterol reductase, which catalyzes the final step in cholesterol synthesis. Deficiency of this enzyme leads to accumulation of 7-dehydrocholesterol (7-DHC) and reduced levels of cholesterol in the blood and tissues, disrupting normal embryonic and postnatal development. SLOS affects multiple body systems and presents with a wide clinical spectrum ranging from m
How is Smith-Lemli-Opitz syndrome inherited?
Smith-Lemli-Opitz syndrome follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Smith-Lemli-Opitz syndrome typically begin?
Typical onset of Smith-Lemli-Opitz syndrome is neonatal. Age of onset can vary across affected individuals.
Are there clinical trials for Smith-Lemli-Opitz syndrome?
Yes — 1 recruiting clinical trial is currently listed for Smith-Lemli-Opitz syndrome on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat Smith-Lemli-Opitz syndrome?
7 specialists and care centers treating Smith-Lemli-Opitz syndrome are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.