What Your Test Results Mean:

Carriers typically show no symptoms of SLOS; however, carriers are at an increased risk of having a child with SLOS. Risk for the current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor.

Disease Explained:

SLOS is an inherited condition characterized by small head size, developmental delays, intellectual disability or learning problems, autism-like behavioral problems, heightened sun sensitivity, and mid-line birth defects. The disorder affects the body’s ability to produce cholesterol. Cholesterol is important for pre- and post-natal development because it is a structural component of cell membranes and the protective substance covering nerve cells (myelin), and also plays a role in the production of certain hormones and digestive acids. Treatment for SLOS is symptomatic. Life expectancy is less than two years in the most severe forms of the disorder but is dependent on the presence of severe symptoms.

How the Genetics Works:

The clinical features of SLOS can be explained by pathogenic variants in the DHCR7 gene. In general, individuals have two copies of the DHCR7 gene. Carriers of SLOS have a single variant in one copy of the DHCR7 gene while individuals with SLOS have variants in both copies of their genes, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.