Elevated circulating 7-dehydrocholesterol concentration

What it means

Concentration of 7-dehydrocholesterol in the blood circulation above the upper limit of normal.

Elevated 7-dehydrocholesterol levels occur as the result of a deficiency of the enzyme delta-7-sterol reductase, the penultimate enzyme of mammalian sterol biosynthesis that converts 7-dehydrocholesterol (7-DHC) to cholesterol. This enzyme removes the C(7-8) double bond introduced by the sterol delta8-delta7 isomerases. In addition, its role in drug-induced malformations is known: inhibitors of the last step of cholesterol biosynthesis such as AY9944 and BM15766 severely impair brain development. Homozygous mutations in the gene encoding for this enzyme are the molecular genetic cause of Smith-Lemli-Opitz Syndrome.

Rare diseases that can present with this1

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Elevated levels of cholesta-5,7-dien-3beta-ol