Clinical Use: Used in the diagnosis of several conditions that has been described in which a genetic defect causes a reduction of a specific enzyme in the synthetic pathway leading to cholesterol or bile acids.
Background: Smith-Lemli-Opitz syndrome – Low activity of 7-DHC reductase enzyme leads to very low cholesterol concentrations and an increase in cholesterol precursors including 7- Dehydrocholesterol. This condition affects 1 in 20000 to 1 in 40000 live births. Patients may be mildly affected with learning and behavioural problems or severely affected with multiple congenital abnormalities resulting in stillbirth or death in the first few weeks of life.

Desmosterolosis – 24-dehydrocholesterol reductase deficiency leads to accumulation of desmosterol, which is associated with multiple abnormalities including failure to thrive, psychomotor retardation, microcephaly and spasticity.

Cerebrotendinous Xanthomatosis – Is a lipid storage disorder in which the synthetic block is due to sterol 27-hydroxylase deficiency which leads to impaired synthesis of chenodeoxycholic acid from cholesterol, increased levels of cholestanol result. Features of the disease include infantile diarrhoea, cataracts, brittle bones and neurological problems. Xanthomas in tendons begin to form in early adulthood. Incidence is 3 – 5/100,000 and more common in the Moroccan Jewish population.

Reference Ranges:
Sitosterol 0 – 13 umol/L 7-Dehydrocholesterol 0.5 – 7.0 µmol/L Cholesterol 1200 – 1700 µmol/L Cholestanol (paediatrics) 1.0 – 9.0 µmol/L Cholestanol (adults) 4.0 – 18.0 µmol/L (Cholestanol reference ranges in MLTG CHOLST in free text.)
Associated Diseases:
Patient Preparation: None required
Specimen Requirements: Whole blood – Lithium Heparin or Plain (red) Tube OR Guthrie card is suitable for analysis.
Turnaround Time: 4 weeks
Additional Information:
Referred Test: Referred test
Location: Sir James Spence Institute