Cerebrotendinous xanthomatosis caused by two new mutations of the sterol-27-hydroxylase gene that disrupt mRNA splicing

Clinical, biochemical, and molecular insights into Cerebrotendinous Xanthomatosis: A nationwide study of 100 Turkish individuals

OBJECTIVE

Cerebrotendinous xanthomatosis (CTX) is an inherited metabolic disorder characterized by progressive neurologic and extraneurologic findings. The aim of this retrospective, descriptive study was to explore the time of presentation and diagnosis, and to expand the phenotype and genotype of CTX, based on a nationwide and comprehensive series of patients in Turkey.

METHODS

The demographic, clinical, biochemical and genotypic characteristics of the CTX patients were reviewed. Data on molecular analysis, age of onset and diagnosis, diagnostic delay, neurologic and extraneurologic symptomatology, results of plasma cholestanol levels, brain magnetic resonance imaging and electromyography at the time of diagnosis were reviewed.

RESULTS

100 confirmed CTX patients from 72 families were included. The mean age at diagnosis was 28.16 ± 14.28 years, and diagnostic delay was 18.39 ± 13.71 years. 36 patients were diagnosed in childhood. Frequency of intention tremor (p = 0.069), peripheral neuropathy (p = 0.234) and psychiatric manifestations (p = 0.396) did not differ between two groups, demonstrating the high rate in pediatric patients. Three adult patients showed a milder phenotype without neurologic involvement. Seven patients had normal plasma cholestanol levels despite neurological impairment. Sequencing of the CYP27A1 gene revealed 25 different variants, with a novel c.671_672del variant not previously described in literature.

CONCLUSION

Based on the observations of this Turkish CTX cohort, it is emphasized that the true prevalence of CTX is probably underestimated and that it has a wide spectrum of clinical phenotypes even without neurological impairment. In children, abnormal cerebellar findings, peripheral neuropathy and psychiatric findings associated with intellectual disability have been suggested as warning signs to avoid diagnostic delay. In cases of clinical suspicion, molecular analysis is recommended despite normal plasma cholestanol levels, as severe neurologic involvement may occur in CTX patients without elevated cholestanol levels.

Cerebrotendinous Xanthomatosis patients with late diagnosed in single orthopedic clinic: two novel variants in the CYP27A1 gene

BACKGROUND

Cerebrotendinous Xanthomatosis (CTX) is a rare autosomal recessive lipid storage disorder caused by loss of function variants in the CYP27A1 gene which encodes sterol 27-hydroxylase, on chromosome 2q35. Although the symptoms begin commonly in infancy, CTX diagnosis is often delayed. The aim of this study is to review the orthopedic findings of the disease by providing an overview of the clinical features of the disease. It is to raise awareness of this condition for which early diagnosis and treatment are important.

METHODS

We retrospectively evaluated the clinical, laboratory, radiological, and genetic findings of eight patients from four families who were admitted to our Orthopedics and Traumatology Department between 2017 and 2022 due to bilateral Achilles tendon xanthomas, were found to have high cholestanol and CYP27A1 gene mutations.

RESULTS

The mean age of patients was 37, and five of them were male. The mean age at the onset of symptoms was 9.25 years. The mean age of initial diagnosis was 33.75 years. Between symptom onset and clinical diagnosis, an average delay of 24.5 years was observed. All patients had bilateral Achilles tendon xanthoma. Notably, a novel variant (c.670_671delAA) in CYP27A1 gene was identified in three patients who also presented with peripheral neuropathy and bilateral pes cavus. One patient had osteoporosis and four patients had osteopenia. Five patients had a history of bilateral cataracts. Furthermore, three of the patients had early-onset chronic diarrhea and three of the patients had ataxia. Two of the patients had epilepsy and seven of the patients had behavior-personality disorder. All patients had low intelligence, but none of them had cardiac disease.

CONCLUSION

We present the diagnostic process and clinical features which the largest CTX case series ever reported from single orthopedic clinic. We suggest that patients with normal cholesterol levels presenting with xanthoma being genetically analyzed by testing at their serum cholestanol level, and that all siblings of patients diagnosed with CTX be examined.

Liver transplantation in an infant with cerebrotendinous xanthomatosis, cholestasis, and rapid evolution of liver failure

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is a disorder of bile acid (BA) metabolism due to biallelic mutations in CYP27A1. The deposition of cholesterol and cholestanol in multiple tissues results, manifesting as neurologic disease in adults or older children. Neonatal cholestasis (NC) as a presentation of CTX is rare; it may self-resolve or persist, evolving to require liver transplantation (LT).

METHODS

We present in the context of similar reports an instance of CTX manifest as NC and requiring LT.

RESULTS

A girl aged 4mo was evaluated for NC with normal serum gamma-glutamyl transpeptidase activity. An extensive diagnostic work-up, including liver biopsy, identified no etiology. Rapid progression to end-stage liver disease required LT aged 5mo. The explanted liver showed hepatocyte loss and micronodular cirrhosis. Bile salt export pump (BSEP), encoded by ABCB11, was not demonstrable immunohistochemically. Both severe ABCB11 disease and NR1H4 disease-NR1H4 encodes farsenoid-X receptor, necessary for ABCB11 transcription-were considered. However, selected liver disorder panel sequencing and mass-spectrometry urinary BA profiling identified CTX, with homozygosity for the predictedly pathogenic CYP27A1 variant c.646G > C p.(Ala216Pro). Variation in other genes associated with intrahepatic cholestasis was not detected. Immunohistochemical study of the liver-biopsy specimen found marked deficiency of CYP27A1 expression; BSEP expression was unremarkable. Aged 2y, the girl is free from neurologic disease.

CONCLUSIONS

Bile acid synthesis disorders should be routinely included in the NC/"neonatal hepatitis" work-up. The mutually supportive triple approach of BA profiling, immunohistochemical study, and genetic analysis may optimally address diagnosis in CTX, a treatable disease with widely varying presentation.

Patients with cerebrotendinous xanthomatosis diagnosed with diverse multisystem involvement

Cerebrotendinous xanthomatosis (CTX) is a lipid storage disease caused by deficiency of sterol 27-hydroxylase enzyme encoded by CYP27A1 gene. This multicenter, cross-sectional descriptive study aimed to document clinical characteristics of CTX patients of different ages, clinical presentations of early-diagnosed patients, and responses to short-term chenodeoxycholic acid (CDCA) treatment. Seven of 11 CTX patients were diagnosed in childhood. Three patients (27%) had neonatal cholestasis, seven (63%) patients had a history of frequent watery defecation started in infantile period, and eight (72.7%) patients had juvenile cataract. Four patients in the adult age group had pyramidal signs and parkinsonism symptoms. The mean Mignarri score at diagnosis was significantly lower in the pediatric patients (267.8 ± 51.4) than in the adult patients (450.0 ± 64.0, p = 0.001). No significant difference was determined between pediatric patients and adult patients regarding plasma cholestanol concentration at diagnosis (p = 0.482). The frequency of defecation decreased with treatment in six children, who had diarrhea at admission. Compared to pretreatment values, patients' body weight and standardized body mass index significantly increased at the 12th month of treatment. In conclusion, Mignarri scores are lower in the pediatric patients than in adult patients since the most determinative signs of the CTX disease are not apparent yet in the childhood. The disease is frequently overlooked in routine practice as the disease presents itself with different clinical combinations both in adults and in children. CTX is potentially a treatable disease; thereby, enhanced awareness is critically important for early diagnosis particularly in children.

Clinical and Genetic Characteristics of Splicing Variant in CYP27A1 in an Iranian Family with Cerebrotendinous Xanthomatosis

Background:

CTX is a rare congenital lipid-storage disorder, leading to a progressive multisystem disease. CTX with autosomal recessive inheritance is caused by a defect in the CYP27A1 gene. Chronic diarrhea, tendon xanthomas, neurologic impairment, and bilateral cataracts are common symptoms of the disease.

Methods:

Three affected siblings with an initial diagnosis of non-syndromic intellectual disability were recruited for further molecular investigations. To identify the possible genetic cause(s), WES was performed on the proband. Sanger sequencing was applied to confirm the final variant. The clinical and molecular genetic features of the three siblings from the new CTX family and other patients with the same mutations, as previously reported, were analyzed. The CYP27A1 gene was also studied for the number of pathogenic variants and their location.

Results:

We found a homozygous splicing mutation, NM_000784: exon6: c.1184+1G>A, in CYP27A1 gene, which was confirmed by Sanger sequencing. Among the detected pathogenic variants, the splice site mutation had the highest prevalence, and the mutations were mostly found in exon 4.

Conclusion:

This study is the first to report the c.1184+1G>A mutation in Iran. Our findings highlight the other feature of the disease, which is the lack of relationship between phenotype and genotype. Due to nonspecific symptoms and delay in diagnosis, CYP27A1 genetic analysis should be the definitive method for CTX diagnosis.

Severe Neonatal Cholestasis in Cerebrotendinous Xanthomatosis: Genetics, Immunostaining, Mass Spectrometry

OBJECTIVES

Cerebrotendinous xanthomatosis (CTX) is caused by defects in sterol 27-hydroxylase (CYP27A1, encoded by CYP27A1), a key enzyme in the bile acid synthesis pathway. CTX usually presents as neurologic disease in adults or older children. The rare reports of CTX manifest as neonatal cholestasis assess the cholestasis as transient, with patient survival. Our experience differs.

METHODS

Homozygous or compound heterozygous CYP27A1 mutations were detected in 8 neonatal cholestasis patients by whole exome sequencing, panel sequencing, or Sanger sequencing. Their clinical and biochemical data were retrospectively reviewed. Immunostaining for CYP27A1 was conducted in liver of 4 patients. Mass spectrometry was used to analyze patients' urine samples.

RESULTS

All 8 infants had severe cholestasis. Five died from, or were transplanted for, liver failure; 3 cleared their jaundice eventually. Marking for CYP27A1 was weak or absent in 3 of the 4 patient specimens. Mass spectrometry of urine revealed a predominance of sulfated and doubly conjugated (sulfated-glucuronidated) bile alcohols. No patient harbored a putatively pathogenic mutation in genes other than CYP27A1 that have been implicated in cholestatic liver disease.

CONCLUSIONS

CTX manifest as neonatal cholestasis has a bile acid profile different from CTX manifest in later life, and thus may be overlooked. Immunostaining, mass spectrometry of urine, and genetic studies can support one another in making the diagnosis. A substantial proportion of CTX patients with severe neonatal cholestasis may die or need liver transplantation. CTX manifest in infancy as severe cholestasis warrants further investigation of biochemical diagnostic criteria and best management.

Juvenile cataract morphology in 3 siblings not yet diagnosed with cerebrotendinous xanthomatosis

PURPOSE

Cerebrotendinous xanthomatosis is a progressive neurodegenerative storage disease caused by recessive CYP27A1 mutations and is characterized by abnormal deposition of cholestanol and cholesterol in multiple tissues, including the lens and brain. Oral chenodeoxycholic acid is preventive and can be therapeutic, but is not used optimally because the condition typically is diagnosed late or not at all. When affected children demonstrate lens opacities, ophthalmologists have the unique potential to facilitate earlier diagnosis and treatment by recognizing the juvenile cataract phenotype. This study highlights the morphology of lens opacities in a family with genetically confirmed disease.

DESIGN

Prospective case series.

PARTICIPANTS

Four siblings and their 2 parents, who are first cousins.

METHODS

Ophthalmic examination, general physical examination, and exome sequencing guided by homozygosity analysis.

MAIN OUTCOME MEASURES

Ophthalmic findings, general clinical findings, and results of CYP27A1 candidate gene testing.

RESULTS

Two sisters, each visually symptomatic before 10 years of age, had a unique pattern of bilateral fleck deposits throughout the lens with significant posterior capsular cataract. When initially examined at 8 years of age, their then-asymptomatic younger brother had the same bilateral fleck deposits with minimal posterior capsular opacity; 1 year later, he demonstrated anterior capsular opacity and became symptomatic. Both asymptomatic parents had few but distinct similar flecks localized at or near the anterior Y-suture, whereas an asymptomatic sister did not. Genetic analysis revealed homozygosity for a known CYP27A1 mutation (c.1263+1G → A) in the 3 symptomatic siblings, heterozygosity for the mutation in the 2 parents, and no mutation in the asymptomatic sister. When specifically questioned, the 3 affected children had experienced recurrent bouts of diarrhea in early childhood, which is a common feature of the disease.

CONCLUSIONS

An unusual pattern of fleck lenticular deposits was seen in affected children. With time, capsular opacities (posterior only or posterior and anterior) developed and caused visual symptoms. Such juvenile lenticular findings should raise suspicion for this treatable metabolic disorder, especially when in the context of recurrent diarrhea during early childhood. Asymptomatic fleck-like opacities at or near the anterior Y-suture may be a carrier sign.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Monitoring of 7α-hydroxy-4-cholesten-3-one during therapy of cerebrotendinous xanthomatosis: a case report

Cerebrotendinous xanthomatosis (CTX) is a rare, inherited autosomal-recessive lipid-storage disorder caused by 27-hydroxylase deficiency. In this study, we report of a 30-year old man with this disorder who was treated using chenodeoxycholic acid, simvastatin, and low-density lipoprotein (LDL) apheresis. The LDL apheresis was performed weekly for nine months. The first subjective improvement was reported by the patient after his fourth LDL-apheresis. Spasticity, gait disturbances, and his entire psychomotoric test results had improved tremendously. His fine motoric skills have been regained. The efficacy of LDL-apheresis was monitored using quantitative determination of 7α-OH-4-cholesten-3-one in plasma based on a LC-MS/MS method. The clearance efficacy of 7α-hydroxy-4-cholesten-3-one from the patient's plasma per LDL-apheresis varied between 8% and 53% but returned to the initial high levels after seven days (mean value 241 ng/mL). A slight negative trend in the plasma concentration could be derived over the period of nine months.

A novel mutation in the sterol 27-hydroxylase gene of a woman with autosomal recessive cerebrotendinous xanthomatosis

Article abstract

Mutations of the gene encoding the mitochondrial enzyme sterol 27-hydroxylase (CYP27A1 gene) cause defects in the cholesterol pathway to bile acids that lead to the storage of cholestanol and cholesterol in tendons, lenses and the central nervous system. This disorder is the cause of a clinical syndrome known as cerebrotendinous xanthomatosis (CTX). Since 1991 several mutations of the CYP27A1 gene have been reported. We diagnosed the clinical features of CTX in a caucasian woman. Serum levels of cholestanol and 7α-hydroxycholesterol were elevated and the concentration of 27-hydroxycholesterol was reduced. Bile alcohols in the urine and faeces were increased. The analysis of the CYP27A1 gene showed that the patient was a compound heterozygote carrying two mutations both located in exon 8. One mutation is a novel four nucleotide deletion (c.1330-1333delTTCC) that results in a frameshift and the occurrence of a premature stop codon leading to the formation of a truncated protein of 448 amino acids. The other mutation, previously reported, is a C - > T transition (c. c.1381C > T) that converts the glutamine codon at position 461 into a termination codon (p.Q461X). These truncated proteins are expected to have no biological function being devoid of the cysteine residue at position 476 of the normal enzyme that is crucial for heme binding and enzyme activity.

Cerebrotendinous xanthomatosis: a critical update

Cerebrotendinous xanthomatosis (CTX) also known as van Bogaert–Scherer–Epstein syndrome, Thiebaut’s syndrome and cerebrotendinous cholesterosis, is an autosomal-recessive lipid-storage disease characterized by the triad of juvenile cataracts, tendon xanthomas and progressive neurodegeneration. Excess cholesterol and cholestanol are deposited in multiple organs, including the cerebrum, cerebellum, lens and tendons. Approximately 300 cases are reported worldwide, but it is suspected that the incidence of CTX is underestimated. The disease is attributed to approximately 50 mutations in the CYP27A1 gene coding for the enzyme sterol 27-hydoxylase, which is responsible for initial oxidation of the side chain of the cholesterol molecule in bile acid biosynthesis. CTX has varied clinical presentations, but no genotype–phenotype relationship has been documented. In some intrafamilial cases, clinical presentations may vary considerably. MRI for CTX is sensitive for diagnosis and classically demonstrates cerebral and cerebellar atrophy and xanthomatous lesions preferentially affecting the dentate nuclei. Patients have high serum levels of cholestanol with normal total cholesterol and increased urinary excretion of bile acids. Treatment of patients with chenodeoxycholic acid, particularly when used along with HMG-CoA reductase inhibitors (statins) or low-density lipoprotein apheresis, can normalize cholestanol levels as well as prevent further degeneration. Therefore, the need for early diagnosis is well documented in the literature, as it prevents the significant morbidity and mortality associated with this disease.

Alternative splicing within the human cytochrome P450 superfamily with an emphasis on the brain: the convolution continues

The human cytochrome P450 (CYP) superfamily of enzymes regulate hepatic phase 1 drug metabolism and subsequently play a significant role in pharmacokinetics, drug discovery and drug development. Alternative splicing of the cytochrome CYP gene transcripts enhances gene diversity and may play a role in transcriptional regulation of certain CYP proteins. Tissue-specific alternative splicing of CYPs is significant for its potential to add greater dimension to differential drug metabolism in hepatic and extrahepatic tissues, such as the brain, and to our understanding of the CYP family. This review provides an overview of tissue-specific splicing patterns, splicing types, regulation and the functional diversities between liver and splice variant CYP proteins and further explores the relevance of tissue-specific alternative splicing of CYPs in the nervous system.

Structural motif-based homology modeling of CYP27A1 and site-directed mutational analyses affecting vitamin D hydroxylation

Human CYP27A1 is a mitochondrial cytochrome P450, which is principally found in the liver and plays important roles in the biological activation of vitamin D(3) and in the biosynthesis of bile acids. We have applied a systematic analysis of hydrogen bonding patterns in 11 prokaryotic and mammalian CYP crystal structures to construct a homology-based model of CYP27A1. Docking of vitamin D(3) structures into the active site of this model identified potential substrate contact residues in the F-helix, the beta-3 sheet, and the beta-5 sheet. Site-directed mutagenesis and expression in COS-1 cells confirmed that these positions affect enzymatic activity, in some cases shifting metabolism of 1alpha-hydroxyvitamin D(3) to favor 25- or 27-hydroxylation. The results suggest that conserved hydrophobic residues in the beta-5 hairpin help define the shape of the substrate binding cavity and that this structure interacts with Phe-248 in the F-helix. Mutations directed toward the beta-3a strand suggested a possible heme-binding interaction centered on Asn-403 and a structural role for substrate contact residues Thr-402 and Ser-404.

Transcriptional regulation of human CYP27 integrates retinoid, peroxisome proliferator-activated receptor, and liver X receptor signaling in macrophages

Cholesterol uptake and efflux are key metabolic processes associated with macrophage physiology and atherosclerosis. Peroxisome proliferator-activated receptor gamma (PPARgamma) and liver X receptor alpha (LXRalpha) have been linked to the regulation of these processes. It remains to be identified how activation of these receptors is connected and regulated by endogenous lipid molecules. We identified CYP27, a p450 enzyme, as a link between retinoid, PPARgamma, and LXR signaling. We show that the human CYP27 gene is under coupled regulation by retinoids and ligands of PPARs via a PPAR-retinoic acid receptor response element in its promoter. Induction of the enzyme's expression results in an increased level of 27-hydroxycholesterol and upregulation of LXR-mediated processes. Upregulated CYP27 activity also leads to LXR-independent elimination of CYP27 metabolites as an alternative means of cholesterol efflux. Moreover, human macrophage-rich atherosclerotic lesions have an increased level of retinoid-, PPARgamma-, and LXR-regulated gene expression and also enhanced CYP27 levels. Our findings suggest that nuclear receptor-regulated CYP27 expression is likely to be a key integrator of retinoic acid receptor-PPARgamma-LXR signaling, relying on natural ligands and contributing to lipid metabolism in macrophages.

Cholestanol Metabolism, Molecular Pathology, and Nutritional Implications

Cholestanol, not cholesterol, is a minor component in the human body and in foods, but an increase in cholestanol concentration in serum induces a pathological condition named cerebrotendinous xanthomatosis (CTX). In our investigation of this disease for more than 25 years, a procedure for quantification of cholestanol by high-performance liquid chromatography and an assay method for sterol 27-hydroxylase were established, and several mutations of the CYP 27 gene in 10 CTX families were identified. We also established experimental animal models with symptoms of CTX by feeding a high cholestanol diet. Corneal dystrophy and gallstones were produced in mice, and an apoptosis of cerebellar neuronal cells was observed in rats. We propose the following underlying mechanism of CTX pathogenesis: When cholesterol in the plasma membrane is replaced by cholestanol to some extent, the membrane fluidity is reduced, and the calcium channel fails to open, inducing cell death. CTX patients are treated with oral administration of chenodeoxycholic acid, which reduces the cholestanol concentration in serum. Cholestanol has a toxic effect, and an imbalance of the cholesterol/cholestanol ratio in plasma membrane is suspected to cause the disturbance of calcium channel function of the membrane.

Two novel mutations in the sterol 27-hydroxylase gene causing cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare recessive autosomal disease caused by mutations of the sterol 27-hydroxylase gene. Clinically, CTX is characterized by tendon xanthomas, cataracts and progressive neurological deficits. Because of the disruption of the 27-hydroxylase activity, CTX patients have elevated plasma levels of cholestanol, a by-product of abnormal bile acid synthesis. The present authors describe a female patient with CTX. The proband in this study presented with elevated cholestanol levels, markedly reduced mitochondrial 27-hydroxylase activity and altered bile acid composition. The 27-hydroxylase gene was analysed for mutations by polymerase chain reaction amplification of the exons and the splice-junction regions of the gene. The proband was found to be a compound heterozygote for two different mutations which have not been previously described: (1) a G --> A transition at nucleotide 455 that is responsible for converting a glycine to a glutamic acid residue at amino acid position 112 (G112E); and (2) a five-nucleotide deletion in exon 5 (from nucleotide 965 to 969) that is responsible for a shift in the reading frame and the insertion of a premature codon at position 296, and consequently, the synthesis of a truncated protein lacking the heme-binding and andrenodoxin-binding domains. Long-term (18-year) treatment of the proband with chenodeoxycholic acid (750 mg day-1) has been effective in preventing any progression of the disease.

Cerebrotendinous xanthomatosis: heterogeneity of clinical phenotype with evidence of previously undescribed ophthalmological findings

Cerebrontendinous xanthomatosis (CTX) is a rare autosomal recessive neurometabolic disease involving lipid metabolism. The classical phenotype is characterized by neurological dysfunction, tendon xanthomas and juvenile cataracts. Other ophthalmological findings have occasionally been reported. To gain more insight into the type and frequency of ophthalmological alterations in this multisystem metabolic disorder, we examined 13 CTX patients. Besides cataracts, found in all cases, the second most frequent ocular abnormality was paleness of the optic disk, which was found in 6 patients and was probably previously underestimated. Signs of premature retinal senescence were also observed. We discuss the possible relation between these ocular manifestations and the metabolic defect.

Cerebrotendinous xanthomatosis. Controversies about nerve and muscle: observations in ten patients

Neuromuscular characteristics were documented in ten patients with biochemically and genetically confirmed cerebrotendinous xanthomatosis. An array of genotypes was found in these patients. Only one patient complained of muscle weakness, while clinical signs of peripheral neuropathy were present in six patients. Electromyogram showed predominantly axonal neuropathy in seven patients. Neurogenic changes were seen in muscle biopsies of nine patients. Sural nerve biopsies of three patients showed features of axonal neuropathy. In addition, in one patient, extensive onion bulb formation was seen, which is indicative of a primarily demyelinating process. Five patients had normal mitochondrial respiratory chain enzyme activity. It is concluded that myopathy is not a feature of cerebrotendinous xanthomatosis and that the most prominent neuromuscular abnormality is sensorimotor axonal polyneuropathy.

Clinical and molecular genetic characteristics of patients with cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a lipid storage disease caused by a deficiency of the mitochondrial enzyme 27-sterol hydroxylase (CYP 27), due to mutations in its gene. In this study we report on mutations in 58 patients with CTX out of 32 unrelated families. Eight of these were novel mutations, two of which were found together with two already known pathogenic mutations. Twelve mutations found in this patient group have been described in the literature. In the patients from 31 families, mutations were found in both alleles. In the literature, 28 mutations in 67 patients with CTX out of 44 families have been described. Pooling our patient group and the patients from the literature together, 37 different mutations in 125 patients out of 74 families were obtained. Identical mutations have been found in families from different ethnic backgrounds. In 41% of all the patients, CYP 27 gene mutations are found in the region of exons 6-8. This region encodes for adrenodoxin and haem binding sites of the protein. Of these 125 patients, a genotype-phenotype analysis was done for 79 homozygous patients harbouring 23 different mutations, out of 45 families. The patients with compound heterozygous mutations were left out of the genotype-phenotype analysis. The genotype-phenotype analysis did not reveal any correlation.

Effect of simvastatin in addition to chenodeoxycholic acid in patients with cerebrotendinous xanthomatosis

The effects of combination therapy with chenodeoxycholic acid (CDCA) and simvastatin on serum cholestanol, low-density lipoprotein (LDL) cholesterol, and lathosterol levels were investigated in seven adult patients with cerebrotendinous xanthomatosis (CTX) who were on long-term treatment with CDCA. The patients were treated with a combination of CDCA 750 mg daily and an increasing dose of simvastatin from 10 mg to 40 mg daily for a period of 6 months. We found a significant effect of this combination therapy compared with CDCA alone in terms of decreasing the serum cholestanol and LDL cholesterol levels, particularly with a daily dose of 40 mg simvastatin. The mean cholestanol level decreased from 9.27 micromol/L (baseline) to 6.69 micromol/L (40 mg simvastatin), while the mean LDL cholesterol level decreased from 5.08 mmol/L (baseline) to 3.04 mmol/L (40 mg simvastatin). No side effects were reported, and there were no effects on the clinical condition, cerebral magnetic resonance imaging (MRI), visual evoked potentials, and electroencephalographic features. We conclude that a combination of 750 mg CDCA and 40 mg simvastatin daily is effective to further reduce serum cholestanol, LDL cholesterol, and lathosterol in adult CTX patients treated with long-term CDCA. Whether this combination treatment will be effective for the long-term prevention of neurological deterioration and atherosclerosis remains to be established.