You are examining a patient you suspect is afflicted with Smith-Lemli-Opitz syndrome (SLOS), which is associated with mild to severe developmental abnormalities. Knowing that this disorder is the consequence of a defect in cholesterol biosynthesis, measurement of the blood levels of which of the following compounds would be most diagnostic of SLOS?
A) acetyl-CoA
B) 7-dehydrocholesterol
C) HMG-CoA
D) lanosterol
E) mevalonate

Question

Quizplus · Accepted Answer

Smith-Lemli-Opitz syndrome is caused by a deficiency in the enzyme 7-dehydrocholesterol reductase, leading to an accumulation of 7-dehydrocholesterol in the blood. Measuring elevated levels of 7-dehydrocholesterol is diagnostic for SLOS.  Smith-Lemli-Opitz syndrome is caused by mutations in the gene encoding the terminal enzyme in cholesterol biosynthesis, that is, 7-dehydrocholesterol reductase. The enzyme converts 7-dehydrocholesterol to cholesterol. Therefore, defects in this gene result in increased serum levels of 7-dehydrocholesterol and reduced levels (15%-27% of normal) of cholesterol.

You Are Examining a Patient You Suspect Is Afflicted with Smith-Lemli-Opitz