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.
Specialty: Genetics