Unique patient with cerebrotendinous xanthomatosis. Evidence for presence of a defect in a gene that is not identical to sterol 27-hydroxylase

Natural history of neurological abnormalities in cerebrotendinous xanthomatosis

OBJECTIVES

Cerebrotendinous xanthomatosis (CTX) is a rare inherited neurodegenerative disorder in bile acid synthesis. The natural history of neurological abnormalities in CTX is not well understood. The object of this study was to determine neurological progression in CTX.

METHODS

A literature search on PubMed for "cerebrotendinous xanthomatosis" yielded 91 publications that reported cases of CTX patients. Two independent reviewers abstracted information about the presence and age of onset of neurological abnormalities in published CTX cases. For each neurological abnormality, we estimated the probability of its onset at any given age using cumulative incidence function analysis. We also present our own case series, in which five CTX patients were evaluated.

RESULTS

The literature search yielded 194 CTX cases (ages ranging from newborn to 67 years old). The most common neurological abnormalities were corticospinal tract abnormalities including weakness, hyperreflexia, spasticity, Babinski sign (59.8%), ataxia (58.8%), cognitive decline (46.4%), and gait difficulty (38.1%); 68 (35.0%) had baseline cognitive problems. Cumulative incidence function analysis revealed that ataxia, gait difficulties, and corticospinal tract abnormalities developed throughout life, while cognitive decline tended to develop later in life. Of the less common neurological abnormalities, seizures, psychiatric changes and speech changes developed throughout life, while parkinsonism and sensory changes tended to develop later in life. Our case series corroborated this temporal pattern of neurological abnormalities.

CONCLUSION

We provide estimates for the neurological progression of CTX, categorizing neurological abnormalities according to time and probability of development. Our approach may be applicable to other rare disorders.

On the formation of 7-ketocholesterol from 7-dehydrocholesterol in patients with CTX and SLO

A new mechanism for formation of 7-ketocholesterol was recently described involving cytochrome P-450 (CYP)7A1-catalyzed conversion of 7-dehydrocholesterol into 7-ketocholesterol with cholesterol-7,8-epoxide as a side product. Some patients with cerebrotendinous xanthomatosis (CTX) and all patients with Smith-Lemli-Opitz syndrome (SLO) have markedly increased levels of 7-dehydrocholesterol in plasma and tissues. In addition, the former patients have markedly upregulated CYP7A1. We hypothesized that these patients may produce 7-ketocholesterol from 7-dehydrocholesterol with formation of cholesterol-7,8-epoxide as a side product. In accord with this hypothesis, two patients with CTX were found to have increased levels of 7-ketocholesterol and 7-dehydrocholesterol, as well as a significant level of cholesterol-7,8-epoxide. The latter steroid was not detectable in plasma from healthy volunteers. Downregulation of CYP7A1 activity by treatment with chenodeoxycholic acid reduced the levels of 7-ketocholesterol in parallel with decreased levels of 7-dehydrocholesterol and cholesterol-7,8-epoxide. Three patients with SLO were found to have markedly elevated levels of 7-ketocholesterol as well as high levels of cholesterol-7,8-epoxide. The results support the hypothesis that 7-dehydrocholesterol is a precursor to 7-ketocholesterol in SLO and some patients with CTX.

Cerebrotendinous xanthomatosis

PURPOSE OF REVIEW

Cerebrotendinous xanthomatosis (CTX) is a rare neurological disease characterized by accumulation of cholesterol and cholestanol in brain and tendons caused by a mutation in the sterol 27-hydroxylase gene (CYP27A1). The mechanism behind the accumulation of cholestanol in the brain was recently clarified and a role of 27-hydroxycholesterol as a regulator of brain cholesterol homeostasis has been established.

RECENT FINDINGS

There is a significant flux of the bile acid precursor 7α-hydroxy-4-cholesten-3-one across the blood-brain barrier in cy27-/- mice with its subsequent conversion into cholestanol. CTX patients with white matter lesions and vacuolation are described. CYP27A1 was identified as a candidate gene for sporadic amyotrophic lateral sclerosis (ALS).

SUMMARY

The mechanism behind accumulation of cholestanol in brain and tendons of patients with CTX has been clarified but it is not known why this accumulation is associated with parallel accumulation of cholesterol and formation of xanthomas. Further studies are needed to understand why some patients with CTX develop white matter lesions in the brain. In view of the fact that CTX can present with upper motor neuronal signs it is interesting that CYP27 has been shown to be a candidate gene for sporadic ALS.

2 Novel deletions of the sterol 27-hydroxylase gene in a Chinese Family with Cerebrotendinous Xanthomatosis

Background

Cerebrotendinous xanthomatosis (CTX) is a rare lipid-storage disease. We investigated the clinic manifestation, histopathology and sterol 27-hydroxylase gene (CYP27A1) in a Chinese family with Cerebrotendinous Xanthomatosis (CTX).

Case Presentation

A 36-year-old female with typical CTX clinical manifestation had Spindle-shaped lipid crystal clefts in xanthomas and "onion-like demyelination" in sural nerve. The patient was compound heterozygote carrying two deletions in exon 1 (c.73delG) and exon 2 (c.369_375delGTACCCA). The family memebers were carriers.

Conclusions

A Chinese family with Cerebrotendinous Xanthomatosis had typical clinical manifestation. CYP27A1 mutations were found in the proband and all other family members.

2 Novel deletions of the sterol 27-hydroxylase gene in a Chinese Family with Cerebrotendinous Xanthomatosis

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is a rare lipid-storage disease. We investigated the clinic manifestation, histopathology and sterol 27-hydroxylase gene (CYP27A1) in a Chinese family with Cerebrotendinous Xanthomatosis (CTX).

CASE PRESENTATION

A 36-year-old female with typical CTX clinical manifestation had Spindle-shaped lipid crystal clefts in xanthomas and "onion-like demyelination" in sural nerve. The patient was compound heterozygote carrying two deletions in exon 1 (c.73delG) and exon 2 (c.369_375delGTACCCA). The family memebers were carriers.

CONCLUSIONS

A Chinese family with Cerebrotendinous Xanthomatosis had typical clinical manifestation. CYP27A1 mutations were found in the proband and all other family members.

Genetic connections between neurological disorders and cholesterol metabolism

Cholesterol is an essential component of both the peripheral and central nervous systems of mammals. Over the last decade, evidence has accumulated that disturbances in cholesterol metabolism are associated with the development of various neurological conditions. In addition to genetically defined defects in cholesterol synthesis, which will be covered in another review in this Thematic Series, defects in cholesterol metabolism (cerebrotendinous xanthomatosis) and intracellular transport (Niemann Pick Syndrome) lead to neurological disease. A subform of hereditary spastic paresis (type SPG5) and Huntington's disease are neurological diseases with mutations in genes that are of importance for cholesterol metabolism. Neurodegeneration is generally associated with disturbances in cholesterol metabolism, and presence of the E4 isoform of the cholesterol transporter apolipoprotein E as well as hypercholesterolemia are important risk factors for development of Alzheimer's disease. In the present review, we discuss the links between genetic disturbances in cholesterol metabolism and the above neurological disorders.