Cerebrotendinous xanthomatosis: defective liver mitochondrial hydroxylation of chenodeoxycholic acid precursors

Update on cerebrotendinous xanthomatosis

PURPOSE OF REVIEW

Cerebrotendinous xanthomatosis (CTX) is a rare genetic lipid storage disorder with highly pleomorphic clinical phenotype. Complications of this disease can be devastating and may include severe cognitive impairment and dementia in later stages. Disease progression can be prevented or stabilized by bile acid replacement therapy, although a subset of patients with advanced disease continue to deteriorate despite therapy.

RECENT FINDINGS

Delayed diagnosis of CTX continues to impede effective treatment. A clinical diagnostic algorithm for CTX was developed that can decrease the age of diagnosis of CTX. The strategy of screening children with bilateral juvenile cataracts for CTX also improved diagnosis, as this group had a 500-fold higher-rate of CTX than the general population. Improved diagnosis of CTX is critical, as patients treated early in the course of the disease have significantly better outcomes compared with those treated later. More sensitive and specific biochemical testing for CTX has been developed that is potentially more informative than blood cholestanol to assess treatment efficacy and medication compliance in CTX.

SUMMARY

Because we are recognizing more severe presentations of CTX in infants and children, and delayed diagnosis and treatment worsens the prognosis, CTX is an excellent candidate disorder for newborn screening using recently reported methods for newborn dried bloodspot analysis.

Cerebrotendinous xanthomatosis; a genetic condition: Clinical profile of three patients from a rural Indian family and review of literature

INTRODUCTION

Cerebrotendinous xanthomatosis is a rare lipid storage disease characterized by infantile onset diarrhea, cataract, tendon xanthomas, and progressive neurologic dysfunction. Cerebrotendinous xanthomatosis is exceptionally rare in Indian population with only few case reports till now.

CASE REPORT

An 18-year-old male presented to orthopedic outpatients clinic with complaints of insidious onset swelling of both achilles over last 3 years, with history of learning and visual difficulties. On examination, there were firm nontender swellings along the course of both tendoachillis. Plantar response was extensor and Romberg test was positive with eyes closed. Cranial MRI showed diffuse cerebral and cerebellar atrophy. Family history showed history of diarrhea, mental retardation, and visual difficulties in his two younger siblings. They were also called upon and evaluated clinically. All three were diagnosed as having cerebrotendinous xanthomatosis based on clinical and radiological features.

CONCLUSION

Cerebrotendinous xanthomatosis is a progressive and preventable disorder and it benefits from therapy, so early diagnosis is mandatory to prevent significant morbidity and mortality associated with this disease.

Bile-acid-induced cell injury and protection

Several studies have characterized the cellular and molecular mechanisms of hepatocyte injury caused by the retention of hydrophobic bile acids (BAs) in cholestatic diseases. BAs may disrupt cell membranes through their detergent action on lipid components and can promote the generation of reactive oxygen species that, in turn, oxidatively modify lipids, proteins, and nucleic acids, and eventually cause hepatocyte necrosis and apoptosis. Several pathways are involved in triggering hepatocyte apoptosis. Toxic BAs can activate hepatocyte death receptors directly and induce oxidative damage, thereby causing mitochondrial dysfunction, and induce endoplasmic reticulum stress. When these compounds are taken up and accumulate inside biliary cells, they can also cause apoptosis. Regarding extrahepatic tissues, the accumulation of BAs in the systemic circulation may contribute to endothelial injury in the kidney and lungs. In gastrointestinal cells, BAs may behave as cancer promoters through an indirect mechanism involving oxidative stress and DNA damage, as well as acting as selection agents for apoptosis-resistant cells. The accumulation of BAs may have also deleterious effects on placental and fetal cells. However, other BAs, such as ursodeoxycholic acid, have been shown to modulate BA-induced injury in hepatocytes. The major beneficial effects of treatment with ursodeoxycholic acid are protection against cytotoxicity due to more toxic BAs; the stimulation of hepatobiliary secretion; antioxidant activity, due in part to an enhancement in glutathione levels; and the inhibition of liver cell apoptosis. Other natural BAs or their derivatives, such as cholyl-N-methylglycine or cholylsarcosine, have also aroused pharmacological interest owing to their protective properties.

Cerebrotendinous xanthomatosis: report of two Brazilian brothers

Cerebrotendinous xanthomatosis is a treatable rare autossomal recessive disease characterized by lipid storage secondary to a sterol 27-hydroxylase deficiency in the formation of cholic and chenodeoxycholic acids. We describe two Brazilian brothers with cognitive impairement and chronic diarrhea. One of them also presents bilateral cataracts. Neurological findings were progressive walking deficit, limb ataxia and pyramidal signs. Both patients had bilateral Achilles tendon xanthomata. Magnetic resonance image showed signal alterations in cerebellar hemispheres. We describe these cases with molecular genetic analysis confirming diagnosis and comparing with previous literature. The CYP27A1 gene study showed a C1187T mutation on exon 6.

Cerebrotendinous xanthomatosis: the spectrum of imaging findings and the correlation with neuropathologic findings

PURPOSE

To describe imaging findings and their neuropathologic correlate in patients with cerebrotendinous xanthomatosis (CTX).

MATERIALS AND METHODS

Computed tomographic (CT) and magnetic resonance (MR) images in 24 patients with symptoms (mean age at time of imaging, 37 years; mean disease duration, 18 years) were reviewed for site and frequency of brain, spinal cord, and Achilles tendon involvement. Two patients died, and imaging findings were compared with postmortem neuropathologic findings.

RESULTS

Apart from nonspecific supratentorial atrophy and deep white matter changes, more typical hyperintense lesions were seen on T2-weighted images in the dentate nucleus (in 79% of patients), globus pallidus, substantia nigra, and inferior olive and extended into adjacent white matter as disease progressed. In these locations, lipid crystal clefts and perivascular macrophages, neuronal loss, demyelination, fibrosis, and reactive astrocytosis were found at microscopic examination. Hypointensity was sometimes found on T2-weighted images in the dentate nucleus and was related to deposition of hemosiderin and calcifications. CT depicted fewer lesions; all had low attenuation, except for the calcifications. Spinal cord MR imaging revealed increased signal intensity in the lateral and dorsal columns on T2-weighted images. Achilles tendon xanthomas displayed intermediate signal intensity on T1- and T2-weighted images.

CONCLUSION

The typical pattern of MR imaging findings reflects the classic histopathologic findings and should prompt the diagnosis of CTX.

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.

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.

Pulmonary lymphangioleiomyomatosis and cerebrotendinous xanthomatosis: is there a link?

A 41-year-old woman had progressive shortness of breath. Cerebrotendinous xanthomatosis was diagnosed 4 years before. An open-lung biopsy showed the simultaneous presence of cerebrotendinous xanthomatosis and pulmonary lymphangioleiomyomatosis. This is perhaps the first time the coincidental occurrence of these two diseases is described.

Bile acids in deermice lacking liver alcohol dehydrogenase

Liver alcohol dehydrogenase (EC 1.1.1.1) is believed to catalyze the oxidation of 26-hydroxylated intermediates in the biosynthesis of bile acids from cholesterol. We have therefore analyzed the composition and size of the bile acid pool in deer-mice genetically lacking alcohol dehydrogenase. Cholic acid was found to be the major primary bile acid accompanied by small amounts of chenodeoxycholic acid. Variable amounts of secondary bile acids were also present, mainly deoxycholic acid and 3 alpha, 12 alpha-dihydroxy-7-oxo-5 beta-cholanoic acid. The same bile acids were found in animals with normal levels of alcohol dehydrogenase. The pool of bile acids in the gallbladder, small intestine and large intestine varied between 4.2 and 8.4 mumol in four animals lacking alcohol dehydrogenase and between 6.0 and 8.4 mumol in four control animals. Ethanol did not influence pool size or composition of bile acids in the animal studied. It is concluded that alcohol dehydrogenase is not obligatory for normal bile acid biosynthesis.

Identification of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 25, 26-pentol in cerebrotendinous xanthomatosis

An unrecognized pentahydroxy bile alcohol has been isolated from the bile and feces of patients with cerebrotendinous xanthomatosis (CTX). Its structure, 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 25, 26-pentol has been deduced by spectroscopic methods and confirmed by comparison with a synthetic analog.