A unique patient with coexisting cerebrotendinous xanthomatosis and β-sitosterolemia

An adult Chinese man presented with tendinous and tuberous xanthomatosis and severe atheromatous changes in the coronary arteries. In addition, he had chronic hemolytic anemia, with spherostomatocytic erythrocytes. Cerebrotendinous xanthomatosis was diagnosed on the basis of increased cholestanol levels in his plasma, red cells and xanthoma, and changes in bile acid composition due to the defective synthesis of chenodeoxycholic acid. Coexisting β-sitosterolemia was confirmed by the finding of large amounts of the plant sterols such as β-sitosterol and campesterol. This is the first report of these two rare lipid storage disorders in the same patient.     

A suspicion index for early diagnosis and treatment of cerebrotendinous xanthomatosis

Background

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive lipid storage disorder characterized by a heterogeneous presentation and a broad spectrum of clinical manifestations. Since early diagnosis and replacement therapy with chenodeoxycholic acid can prevent clinical deterioration, our aim was to develop a diagnostic tool to identify and treat CTX patients at an initial stage of the disease.

Methods

We devised a suspicion index, composed of weighted scores assigned to indicators such as family history characteristics and common systemic and neurological features, on the basis of a pooled analysis of selected international CTX series. The indicators were classified as very strong (score 100), strong (50) or moderate (25). The suspicion index was then applied retrospectively to our CTX population.

Results

Early systemic signs such as cataract, diarrhea and neonatal cholestatic jaundice were considered strong indicators, together with neurological features such as intellectual impairment, psychiatric disturbances, ataxia, spastic paraparesis and dentate nuclei abnormalities at MRI. Tendon xanthomas were regarded as very strong indicators, as was an affected sibling. A total score?≥?100 warranted serum cholestanol assessment. Elevated cholestanol or a total score?≥?200, with one very strong or four strong indicators, warranted CYP27A1 gene analysis. In our patients, age at diagnosis was 35.5?±?11.8 years (mean ± standard deviation), whereas with the diagnostic tool it became 10.6?±?9.8 years (p?<?0.01).

Conclusions

Our suspicion index provides a simple and inexpensive diagnostic tool allowing diagnosis and treatment of CTX before neurological disability occurs.     

以胆汁淤积性黄疸发病的新生儿脑腱黄瘤病1例报告

脑腱黄瘤病(cerbrotendinous xanthomatosis,CTX)是由甾醇-27-羟化酶(CYP27A1)基因突变引起的罕见常染色体隐性遗传病,其发病率低,世界范围内发病率为3/10万~5/10万,女性多于男性[1],临床表现多样,易被误诊、漏诊。目前报道的患者大多为成人,儿科报道的较少。现将1例利用全外显子组测序诊断的新生儿CTX报告如下。     

Epidemiology,diagnosis, and treatment of cerebrotendinous xanthomatosis (CTX)

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disorder of bile acid synthesis caused by mutations in the cytochrome P450 CYP27A1 gene that result in production of a defective sterol 27-hydroxylase enzyme. CTX is associated with abnormally high levels of cholestanol in the blood and accumulation of cholestanol and cholesterol in the brain, tendon xanthomas, and bile. Hallmark clinical manifestations of CTX include chronic diarrhea, bilateral cataracts, tendon xanthomas, and neurologic dysfunction. Although CTX is a rare disorder, it is thought to be underdiagnosed, as presenting signs and symptoms may be nonspecific with significant overlap with other more common conditions. There is marked variability in signs and symptoms, severity, and age of onset between patients. The disease course is progressive and potentially debilitating or fatal, particularly with respect to neurologic presentations that can include intellectual disability, autism, behavioral and psychiatric problems, and dementia, among others. Treatment with chenodeoxycholic acid (CDCA; chenodiol) is the current standard of care. CDCA can help restore normal sterol, bile acid, bile alcohol, and cholestanol levels. CDCA also appears to be generally effective in preventing adverse clinical manifestations of the disease from occurring or progressing if administered early enough. Improved screening and awareness of the condition may help facilitate early diagnosis and treatment.     

Clinical and molecular genetic features of cerebrotendinous xanthomatosis patients in Chinese families

Metabolic Brain Disease - Cerebrotendinous xanthomatosis (CTX) is a lipid-storage disease caused by mutations in CYP27A1. Current publications of Chinese CTX were mainly based on case reports. Here...     

Isotopomer spectral analysis of intermediates of cholesterol synthesis in patients with cerebrotendinous xanthomatosis

Four patients with cerebrotendinous xanthomatosis (CTX) and 2 healthy controls received a constant proximal intraduodenal infusion of 1- 13 C-acetate as a stable-isotope-labeled marker of sterol synthesis. One patient was treated with pravastatin (20 mg twice daily) and another patient with chenodeoxycholic acid (250 mg tid). Every hour, venous blood and duodenal samples were obtained. Stable-isotope enrichment of neutral and polar sterols in serum and bile was assessed by gas chromatography/mass spectrometry. Isotopomer spectral analysis was performed on cholesterol, lathosterol, Delta-8-cholesterol, methylsterol, and lanosterol. Stable-isotope labeling of cholestanol, bile acids, and bile alcohols was analyzed by assessing the change over time of the ratio of M + 3 to M + 0. Eleven hours after marker infusion, we found up to 50% newly synthesized lathosterol in serum and up to 80% in bile, with similar results for other cholesterol precursors. In cholesterol, stable-isotope labeling could be demonstrated in all study subjects with a more prominent labeling in bile than in serum. No stable-isotope labeling was detected in cholestanol. Only minor stable-isotope incorporation was detectable in polar sterols in some subjects. Therapy with pravastatin did not have any effect on fractional or absolute synthesis rates or on the concentrations of cholestanol or cholesterol precursors compared to untreated patients with CTX. In contrast, therapy with chenodeoxycholic acid markedly lowered the concentrations of cholestanol and cholesterol precursors, led to a disappearance of bile alcohols, and reduced absolute synthesis rates of lathosterol. Isotopomer spectral analysis proved to be a powerful method to assess the endogenous synthesis of cholesterol precursors in patients with CTX. Higher fractional synthesis in bile than in serum may be due to the size of the pools in bile vs serum. Cholestanol exhibits no marker uptake and is therefore probably synthesized from preformed cholesterol. Biliary cholesterol secretion in patients with CTX is decreased compared to healthy controls.     

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.     

The clinical and imaging features of cerebrotendinous xanthomatosis: A case report and review of the literature

Rationale:Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive lipid deposition disorder characterized by systemic signs and neurological dysfunction. The radiological features of CTX are infrequently summarized in the literature.Patient concerns:We described a 40-year-old male patient who repeatedly engaged in wrestling matches and presented with progressive difficulty in walking and reduced balance with egg-sized, hard, smooth, and painless masses in both ankles.Diagnosis:Neuroimaging examination showed abnormalities both supra- and infratentorially. Bilateral ankle joint magnetic resonance imaging showed bilateral xanthomata of the Achilles tendon. The diagnosis was confirmed by the detection of a sterol 27-hydroxylase gene mutation.Interventions:The patient was treated with chenodeoxycholic acid (250 mg 3 times per day).Outcomes:To date, the patient''s bilateral xanthomas of the Achilles tendon have begun to diminish, and his neurological impairment has not deteriorated further but has not yet improved.Lessons:We report a rare case of CTX and summarize the clinical and imaging features of this disease. Our findings suggest that the abnormal signals in the dentate nucleus or a long spinal cord lesion involving the central and posterior cord, combined with tendon xanthoma, are important clues for the diagnosis of CTX.     

Transformation of 4-cholesten-3-one and 7 alpha-hydroxy-4-cholesten-3-one into cholestanol and bile acids in cerebrotendinous xanthomatosis

In order to determine whether cholestanol and bile acids are derived from the same precursor, key intermediates of both biosynthetic pathways beyond cholesterol were administered intravenously to a patient with cerebrotendinous xanthomatosis and to a control subject. After pulse-labeling with [4-14C]4-cholesten-3-one and [G-3H]7 alpha-hydroxy-4-cholesten-3-one, cholestanol, cholesterol, and the two primary bile acids, cholic acid and chenodeoxycholic acid were isolated from specimens of bile. Each compound was purified by thin-layer chromatography and conclusively identified by gas-liquid chromatography-mass spectrometry. In other studies, the in vitro formation of 4-cholesten-3-one from cholesterol was measured in hepatic microsomal fractions prepared from a subject with cerebrotendinous xanthomatosis and from 3 control individuals. In all subjects, cholic acid and chenodeoxycholic acid were labeled with tritium, but neither cholesterol nor cholestanol contained this isotope. In contrast, 14C was detected in the cholestanol fraction with trace amounts in chenodeoxycholic acid, cholic acid, and cholesterol. Hepatic microsomes prepared from liver biopsy specimens obtained from a subject with cerebrotendinous xanthomatosis produced three times more 4-cholesten-3-one than the controls. The results indicate that 4-cholesten-3-one was converted primarily into cholestanol and 7 alpha-hydroxy-4-cholesten-3-one into cholic acid and chenodeoxycholic acid. Neither ketonic steroid was transformed into cholesterol. The increased production of cholestanol in cerebrotendinous xanthomatosis may be accounted for by enhanced hepatic formation of 4-cholesten-3-one. 7 alpha-Hydroxy-4-cholesten-3-one is a precursor of bile acids, but not of cholestanol.     

Studies of the mechanism of the increased biosynthesis of cholestanol in cerebrotendinous xanthomatosis. The activity of delta 5-3 beta-hydroxysteroid dehydrogenase

It was recently proposed that the increased biosynthesis of cholestanol in cerebrotendinous xanthomatosis (CTX) is due to increased activity of the delta 5-3 beta-hydroxysteroid dehydrogenase involved in bile acid biosynthesis, causing increased conversion of cholesterol into cholestanol through 4-cholesten-3-one. Our attempts to confirm this hypothesis have failed. Liver biopsy specimens from two patients with CTX did not have any increased capacity to catalyze conversion of 7 alpha-hydroxycholesterol into 7 alpha-hydroxy-4-cholesten-3-one. Further, we did not find any changes in the activity of liver microsomal delta 5-3 beta-hydroxysteroid dehydrogenase after feeding rabbits with cholestanol or cholesterol. The findings are discussed in relation to our hypothesis that the accelerated biosynthesis of cholestanol in CTX is due to an increased conversion of early bile acid intermediates into cholestanol.     

Mutations in the sterol 27-hydroxylase gene (CYP27A) cause hepatitis of infancy as well as cerebrotendinous xanthomatosis

Follow-up investigations were undertaken on a previously reported patient who had severe familial giant cell hepatitis in infancy associated with substantially increased urinary excretion of bile alcohol glucuronides. By the age of 11 years, he had developed a profile of cholanoids in plasma and urine that closely resembled the pattern seen in cerebrotendinous xanthomatosis (CTX). Sequencing of the sterol 27-hydroxylase gene (CYP27A) showed that he was homozygous for a deletion (525/526delG) that causes a frameshift and a premature stop codon. This genotype has previously been described in an adult female with classical symptoms of CTX (tendon xanthomata, cataracts and deteriorating cognitive function). A review of past medical histories of a group of patients with CTX revealed that prolonged neonatal cholestatic jaundice was common. The family histories also revealed fetal and neonatal deaths among siblings of patients with CTX. We conclude that defective activity of cholesterol 27-hydroxylase can lead to neonatal cholestatic jaundice ('hepatitis of infancy'), which may be self-limiting. After a latent period, however, progressive accumulation of cholesterol and cholestanol can lead to the xanthomata, neurodegeneration, cataracts and atherosclerosis that are typical of CTX.     

Hydrophilic 7 beta-hydroxy bile acids, lovastatin, and cholestyramine are ineffective in the treatment of cerebrotendinous xanthomatosis

We compared the effect of treatments with hydrophilic bile acids (ursodeoxycholic and ursocholic acids), cholestyramine, and lovastatin versus chenodeoxycholic acid in 4 patients with cerebrotendinous xanthomatosis (CTX). Bile acids and bile alcohols in plasma, bile, and urine before and after treatment were quantitated by gas-liquid chromatography. Untreated, all patients showed abnormal biliary bile acid composition: cholic acid (72.7%) and chenodeoxycholic acid (6.2%), and polyhydroxylated C(27)-bile alcohols (10.0%), and elevated plasma cholestanol levels. Treatment with hydrophobic chenodeoxycholic acid inhibited abnormal bile acid synthesis (virtual disappearance of C(27)-bile alcohols from plasma, bile, and urine and marked reduction of plasma cholestanol levels). Hydrophilic ursodeoxycholic and ursocholic acids did not inhibit abnormal bile acid synthesis, while cholestyramine increased abnormal bile acid synthesis (continued increased formation of polyhydroxylated C(27)-bile alcohols and further elevation of plasma cholestanol levels). Lovastatin did not affect abnormal bile acid synthesis or reduce plasma cholestanol levels. The results demonstrate that impaired side-chain oxidation in bile acid synthesis due to mutations of Cyp27 results in increased formation of polyhydroxylated C(27)-bile alcohols and cholestanol in CTX. Hydrophobic chenodeoxycholic acid, but not cholestyramine, lovastatin, or hydrophilic 7beta-hydroxy acids, inhibited the abnormal synthetic pathway. The role of chenodeoxycholic acid in downregulating abnormal bile acid synthesis in CTX is emphasized.     

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

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disorder believed to be exclusively caused by mutations in the CYP27A1 gene coding for the enzyme sterol 27-hydroxylase. Common findings in CTX are tendon xanthomas, cataracts and progressive neurological dysfunction. Here, we characterize an adult female patient with tendon xanthomas and classic biochemical findings of CTX (i.e. high levels of bile alcohols and cholestanol and extremely low levels of 27-hydroxycholesterol in plasma). Additionally, sterol 27-hydroxylase activity in cultured monocyte-derived macrophages from this patient was <5% of normal. Sequencing the CYP27A1 gene uncovered that the patient is heterozygous for two previously undescribed base substitutions in exon 8, C478A and C479A, which are expected to affect the haeme-binding domain of the enzyme. When expressed in HEK293 cells, the corresponding protein had only 8% of normal enzymatic activity. No other mutation was found in the open reading frame of the CYP27A1 gene, intron-exon boundaries or in the 5'-untranslated region up to 5000 bp distal to the translational start site. Sequencing mRNA isolated from leucocytes from the patient revealed a 1 : 1 ratio of mutated and nonmutated species, with total mRNA levels that were not significantly different from the controls. It is concluded that the patient is heterozygous for two mutations affecting one allele of the CYP27A1 gene and with at least one additional yet undefined gene that is of critical importance for the activity of sterol 27-hydroxylase.