The role of cholesterol biosynthesis and metabolism causing medical complexity in patients with Smith-Lemli-Opitz Syndrome (SLOS)

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive genetic disorder associated with complex anatomic abnormalities, accompanied by medical, developmental and behavioral challenges. It was the first human disorder identified to be caused by an error in the complex cholesterol biosynthetic pathway, more than thirty years ago. This review will cover the clinical and developmental phenotype of patients with SLOS, and the understanding of how cholesterol deficiency, accumulation of the cholesterol precursors 7- and 8-dehydrocholesterol (7-DHC and 8-DHC), and the oxidation of these precursors into toxic oxysterols, are now known to cause this complex phenotype. There is a wide range of severity in patients with SLOS. The most severely affected babies may be miscarried or die in the newborn period due to lethal congenital anomalies. The most mildly impacted patients may show few anatomic abnormalities other than 2–3 toe syndactyly, but still display cognitive and behavioral challenges along the autism spectrum. The review will also cover the medical evaluation and interventions which are recommended in caring for patients with SLOS. There is no cure for this devastating disease, but certain interventions can lead to an improved quality of life, and stabilization of progressive problems for these complex patients.