Cerebrotendinous Xanthomatosis (CTX) is a rare lipid storage disorder that is associated with a number of laboratory findings.


In CTX the breakdown of cholesterol to cholic acid and chenodeoxycholic acid is blocked by a marked reduction in sterol 27-hydroxylase activity. 7-alpha-4-cholesten-3-one accumulates and is broken down to 25-hydroxylated bile alcohol or cholestanol


Laboratory testing may involve:

(1) plasma cholestanol concentration in µg/dL, with ratio to upper limit of normal (ULN)

(2) plasma bile alcohol concentration in nmol/L, with ratio to upper limit of normal (ULN)

(3) urine bile alcohol concentration in nmol/L

(4) sterol 27-hydroxylase activity in leukocytes (a mitochondrial enzyme, may not be readily available)

(5) serum cholesterol in mg/dL, with ratio to upper limit of normal (ULN)

(6) plasma 5-alpha-cholestanol concentration

(7) chenodeoxycholic acid


Laboratory Finding

Findings in CTX

ratio of plasma cholestanol to ULN

>= 5

ratio of bile alcohol concentration to ULN

>= 500

urine bile alcohol concentration

> 10,000 nmol/L (usually undetectable)

sterol 27-hydroxylase activity, with production of chenodeoxycholic acid

markedly reduce

serum cholesterol ratio to ULN

< 1

plasma 5-alpha-cholestanol ratio to ULN

> 1


Other causes of xanthomas often have an elevated serum cholesterol concentration.


Therapy with chenodeoxycholic acid reduces synthesis of bile acid and the accumulation of cholestanol.


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