What is the role of lab tests in the workup of cerebrotendinous xanthomatosis (CTX)?

Updated: Jun 20, 2019
  • Author: Robert D Steiner, MD; Chief Editor: Maria Descartes, MD  more...
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Answer

Laboratory studies in cerebrotendinous xanthomatosis (CTX) include various tests.

Whole blood, serum, and plasma studies

Findings reveal elevated plasma and serum cholestanol levels and low-to-normal cholesterol levels (usually 115-220 mg/dL). The cholestanol level is typically 3-15 times higher than mean levels in unaffected individuals and can range from 1.3-15 mg/dL. [22] The cholesterol-to-cholestanol ratio is said to be a better indicator of disease than cholestanol concentration alone. [49] A low cholesterol-to-cholestanol ratio in the diagnostic range is diagnostic in the appropriate clinical setting; however, additional confirmatory testing is recommended if feasible.

Low-density lipoprotein and triglyceride levels are also usually normal. High-density lipoprotein and very-low density lipoprotein levels vary. Although not typically obtained, bile acid intermediate and other sterol levels are also elevated, such as 7-dehydrocholesterol, [50] 7-alpha-hydroxycholesterol, and lathosterol levels. Some serum bile acid levels themselves are low. Measurement of 7-alpha-hydroxy-4-cholesten-3-one facilitates rapid, convenient diagnostic testing for cerebrotendinous xanthomatosis and may or may not be useful in monitoring treatment response. [51, 52] Measurement of the bile acid precursor (7-alpha, 12-alpha-dihydroxy-4-cholesten-3-one) enables sensitive dried bloodspot testing for cerebrotendinous xanthomatosis, possibly even newborn dried bloodspot testing. [53]

Regardless of whether cerebrotendinous xanthomatosis is suspected clinically, it is increasingly being identified by exome or genome sequencing. [54]


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