TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

Test ID: STER    
Sterols, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Investigation of possible desmosterolosis (desmosterol reductase deficiency), cerebrotendinous xanthomatosis, lathosterolosis, sitosterolemia, sterol C4 methyl oxidase deficiency, MEND (male EBP disorder with neurologic defects) syndrome and X-linked chondrodysplasia punctata 2

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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.

 

Desmosterolosis (desmosterol reductase deficiency) is a very rare disorder of cholesterol biosynthesis with a clinical phenotype similar to that of Smith-Lemli-Opitz (SLO) syndrome (7-dehydrocholesterol reductase deficiency). It is caused by variants in DHCR24 (3-beta-hydroxysterol delta-24-reductase). To date, less than 20 cases of desmosterolosis have been described. Its biochemical marker is the marked elevation of desmosterol in plasma, tissue, and cultured cells.

 

Another very rare disorder of cholesterol biosynthesis is lathosterolosis caused by variants in SC5DL (sterol 3-beta-hydroxysteroid-delta-5-desaturase). Less than 20 patients have been described to date, but the phenotype appears to be characterized by dysmorphic features, multiple congenital anomalies including those of limb and kidney, intellectual disability, and liver disease. Biochemical abnormalities include elevated lathosterol and transaminases, hyperbilirubinemia, and absent 7-dehydrocholesterol.

 

Sitosterolemia is a rare autosomal recessive disorder caused by variants 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.

 

Cerebrotendinous xanthomatosis (CTX), also known as 27-hydroxylase deficiency, is caused by variants in the CYP27A1 gene. CTX is an autosomal recessive sterol storage disease resulting in the accumulation of cholestanol and cholesterol in most tissues and markedly increased levels of cholestanol in serum. Additionally the ketosterol bile acid precursors (7-alpha-hydroxy-4-cholesten-3-one [7a-C4] and 7-alpha,12-alpha–dihydroxycholest-4-en-3-one [7a12aC4]) are elevated in multiple tissues throughout the body and can be measured in blood or plasma (see CTXBS / Cerebrotendinous Xanthomatosis, Blood Spot; CTXWB / Cerebrotendinous Xanthomatosis, Blood; or CTXP / Cerebrotendinous Xanthomatosis, Plasma).

 

Clinical symptoms, which are variable, develop gradually and can include early chronic diarrhea, followed by bilateral cataracts, tuberous and tendon xanthomas, early atherosclerosis, and progressive neurologic impairment such as ataxia, paraparesis, cerebellar ataxia, and dementia. CTX should be suspected in patients with tendon xanthomas and normal or elevated serum cholesterol, and considered in cases of unexplained juvenile cataracts

 

X-linked chondrodysplasia punctata 2 (CDPX2) and MEND (male EBP disorder with neurologic defects) are caused by defects in EBP, which codes for emopamil binding protein, an important enzyme in the final steps of the sterol biosynthesis pathway. CDPX2 is a typically male-lethal X-linked dominant skeletal dysplasia with accompanying skin, hair, nail, and eye abnormalities (ichthyosis in the newborn, scarring alopecia, cataracts). The phenotype in affected females is variable ranging from severe skeletal and internal anomalies leading to fetal demise or stillbirth to milder short stature or even asymptomatic carriers. 

 

MEND syndrome, caused by non-mosaic partial loss of function variants in EBP, affects primarily males. It is a neurologic phenotype characterized by moderate-to-severe developmental delay and central nervous system malformations, in particular Dandy-Walker malformation, agenesis of the corpus callosum, and hydrocephalus. Many patients have dysmorphic features that overlap with Smith-Lemli-Opitz syndrome (2-3 toe syndactyly, postaxial polydactyly, and urogenital anomalies). Females are rarely affected.

 

Biochemical abnormalities for CDXP2 and MEND include elevated 8(9)-cholestenol and 8-dehydrocholesterol.

 

Sterol C4 methyl oxidase deficiency (SC4MOL) is an autosomal recessive inborn error of cholesterol metabolism characterized by microcephaly, congenital cataracts, and psoriasiform dermatitis. Other features include immune dysregulation, joint pain, short stature and intellectual disability. Biochemical abnormalities include increased plasma 4,4'-dimethyl and 4alpha-monomethylsterols such as dihydro T-MAS (4,4'-dimethyl-5alpha-cholesta-8(9)-en-3beta-ol), and decreased total, low-density lipoprotein, and high-density lipoprotein cholesterol.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

7-DEHYDROCHOLESTEROL

< or = 2.0 mg/L

 

8-DEHYDROCHOLESTEROL

< or = 0.3 mg/L

 

8(9)-CHOLESTENOL

< or = 5.0 mg/L

 

CAMPESTEROL

< or = 8.0 mg/L

 

CHOLESTANOL

< or = 6.0 mg/L

 

DESMOSTEROL

< or = 2.5 mg/L

 

DIHYDRO T-MAS

< or = 0.3 mg/L

 

LATHOSTEROL

< or = 6.0 mg/L

 

SITOSTEROL

< or = 15.0 mg/L

 

SQUALENE

< or = 1.0 mg/L

 

STIGMASTEROL

< or = 0.5 mg/L

Interpretation Provides information to assist in interpretation of the test results

A quantitative report of the patient's sterol profile and a Biochemical Genetics consultant's interpretation is provided for each specimen.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Reference ranges were derived using fasting specimens from healthy individuals. Sitosterol and campesterol values may be mildly elevated in individuals whose diets include foods with high concentrations of plant sterols, such as some vegetable oils and infant formulas.

 

Desmosterol may be elevated in individuals on medications containing amiodarone.(1)

 

7-Dehydrocholesterol (7-DHC) and 8-dehydrocholesterol (8-DHC) may be mildly elevated in individuals on certain antidepressant and/or antipsychotic medications such as aripiprazole and trazodone.(2)

 

Patients with primary dyslipidemias may also have altered cholesterol metabolism and mild elevations of sterols.(3)

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Simonen P, Lehtonen J, Lampi AM, et al: Desmosterol accumulation in users of amiodarone. J Intern Med. 2018 Jan;283(1):93-101. doi: 10.1111/joim.12682.

2. Hall P, Michels V, Gavrilov D, et al: Aripiprazole and trazodone cause elevations of 7-dehydrocholesterol in the absence of Smith-Lemli-Opitz syndrome. Mol Genet Metab. 2013 Sep-Oct;110(1-2):176-178

3. Lupatelli G, De Vuono S, Mannarino E: Patterns of cholesterol metabolism: Pathophysiological and therapeutic implications for dyslipidemias and the metabolic syndrome. Nutr Metab Cardiovasc Dis. 2011 Sep;21(9):620-627. doi: 10.1016/j.numecd.2011.04.010

4. Zolotushko J, Flusser H, Markus B, et al: The desmosterolosis phenotype: spasticity, microcephaly and micrognathia with agenesis of corpus callosum and loss of white matter. Eur J Hum Genet. 2011;19(9):942-946. doi: 10.1038/ejhg.2011.74

5. Bjorkhem I, Boberg KM, Leitersdorf El: Inborn errors in bile acid biosynthesis and storage of sterols other than cholesterol. In: Valle D, Beaudet AL, Vogelstein B, eds, et al: The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed November 10, 2020. Available at http://ommbid.mhmedical.com/content.aspx?bookid=971&sectionid=62638585

6. Lu K, Lee MH, Hazard S, et al: Two genes that map to the STSL locus cause sitosterolemia: genomic structure and spectrum of mutations involving sterolin-1 and sterolin-2, encoded by ABCG5 and ABCG8, respectively. Am J Hum Genet. 2001 Aug;69(2):278-290

7. Pilo de la Fuente B, Sobrido MJ, Giros M, et al: Usefulness of cholestanol levels in the diagnosis and follow-up of patients with cerebrotendinous xanthomatosis. Neurologia. 2011;26:397-404

8. Herman GE, Kratz L: Disorders of sterol synthesis: beyond Smith-Lemli-Optiz syndrome. Am J Med Genet C Semin Med Genet. 2012;106C:301-321

9. Kumble S, Savarirayan R: Chondrodysplasia punctata 2, X-linked. In: Adam MP, Ardinger HH, Pagon RA, eds, et al. GeneReviews [Internet]. University of Washington, Seattle; 2011. Updated January 9, 2020. Accessed February 1, 2021. Available at www.ncbi.nlm.nih.gov/books/NBK55062/

10. Parraga I, Lopez-Torres J, Andres F, et al: Effect of plant sterols on the lipid profile of patients with hypercholesterolaemia. Randomised, experimental study. BMC Complement Altern Med. 2011;11:73. doi: 10.1186/1472-6882-11-73