Cholesterol plays an essential role in many cellular and developmental processes. In addition to its role as a membrane lipid, it is the precursor to numerous molecules that play an important role in cell growth and differentiation, protein glycosylation, and signaling pathways. The biosynthesis of cholesterol and its subsequent conversion to other essential compounds is complex, involving a number of intermediates and enzymes. Disorders that result from a deficiency of these enzymes lead to an accumulation of specific intermediates and inhibit the formation of important biomolecules. Clinical findings common to cholesterol biosynthesis disorders include congenital skeletal malformations, dysmorphic facial features, psychomotor retardation, and failure to thrive.
The clinical phenotype of desmosterolosis (desmosterol reductase deficiency) is similar to Smith-Lemli-Opitz (SLO) syndrome (7-dehydrocholesterol reductase deficiency) and typically involves the central nervous system (CNS). Its biochemical marker is the elevation of desmosterol in plasma, tissue, and cultured cells.
Sitosterolemia is a rare autosomal recessive disorder caused by mutations in the ATP-binding cassette (ABC) transporter genes, ABCG5 and ABCG8, which abnormally enhance the absorption of plant sterols and cholesterol from the intestines. Patients often present with hematologic abnormalities and tendon and tuberous xanthomas as well as premature coronary artery disease. A biochemical diagnosis of sitosterolemia is made by documenting elevations of the plant sterols sitosterol and campesterol in plasma or serum.
DESMOSTEROL 0.0-2.0 mg/L
LATHOSTEROL 0.0-3.0 mg/L
CAMPESTEROL 0.0-7.0 mg/L
SITOSTEROL 0.0-5.0 mg/L
CHOLESTANOL 0.0-5.0 mg
Patients with sitosterolemia typically have campesterol values >40 mg/L and sitosterol values >80 mg/L.
A quantitative report of the patient's sterol profile and a Biochemical Genetics consultant's interpretation is provided for each specimen.