Genetic analysis enables definite and rapid diagnosis of cerebrotendinous xanthomatosis

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.

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.

Plexiform xanthomatous tumor: a report of 20 cases in 12 patients

We present 12 patients with 20 plexiform xanthomatous tumors (PXTs). All patients were male. Patient ages ranged from 20 to 59 years (mean 45 years). Clinical information was available for 11 (92%) patients. Only one patient with markedly elevated cholesterol levels had a family history of hypercholesterolemia; none of the others had a family or personal history of diabetes mellitus, hypercholesterolemia, or hyperlipoproteinemia. Three patients had markedly elevated serum triglyceride levels. The tumors were solitary in seven patients and multiple in five patients: three patients had two tumors, one presented had three, and one had four. PXTs were located on the knee (n = 8), elbow (n = 5), foot or hand (n = 3), and one each on the Achilles tendon, buttock, toe, and back. PXT was white to yellow in color and ranged in size from 0.7 to 5 cm (mean 2.7 cm). The tumors were located in the dermis and subcutis, had a distinctive plexiform arrangement, and were composed of various admixtures of uniform epithelioid and xanthomatous cells. All tumors in patients with solitary or multiple lesions had a plexiform architecture. Most of the nodules of the plexiform pattern of PXTs measured 0.5-2 mm. Rarely cholesterol clefts, necrosis, sparse inflammation, and multinucleated Touton giant cells were present. In two patients with multiple tumors, the PXT completely lacked the xanthoma cells and thus resembled an epithelioid lesion. Immunohistochemically, all lesions were KP1 (CD68) and vimentin positive and lysozyme, S-100 protein, HMB-45, epithelial membrane antigen, cytokeratins, factor VIIIrag, CD34, muscle-specific actin, alpha-smooth muscle actin, desmin (D33), desmin (Der-11), chromogranin, synaptophysin, neurofilament protein, and glial fibrillary acidic protein negative. Two patients with multiple lesions noted recurrences over 10 years. With the exception of one patient who died of an unknown cause, all 10 patients with follow-up were alive, some with residual disease, over a mean of 9 years (range 1-25 years). Some PXTs may represent a morphologic variant of tuberous or tendinous xanthoma, yet its exclusive occurrence in men, absence of personal/familial hyperlipemia/hypercholesterolemia in some patients, and relative paucity of inflammation and cholesterol clefts may make this a distinctive entity.

Cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis is a rare autosomal recessive lipid-storage disease caused by mutations in the sterol 27-hydroxylase gene. The accumulation of cholestanol in various tissues characterizes this disease. Diagnosis is based on determination of urinary bile alcohols. Therapy with chenodeoxycholic acid may arrest the progression of the disease. A 55-year-old woman presented with a slowly progressive paraparesia and two firm subcutaneous tumors over the knees. Her medical history revealed difficulty in standing and walking since infancy, bilateral juvenile cataracts, and mental retardation. Histopathologic examination of one subcutaneous tumor was consistent with tendinous xanthoma. Substantial elevation of urinary bile alcohols confirmed the diagnosis. Treatment with oral chenodeoxycholic acid was started, with only mild improvement of spasticity. Recognition of tendon xanthomas in a young patient with neurologic symptoms or cataracts (or both) is crucial to start early treatment and to avoid irreversible neurologic sequelae.

Magnetic resonance imaging and spectroscopic changes in brains of patients with cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare disorder due to an inherited defect in the metabolic pathway of cholesterol. Early diagnosis of the disease is particularly important as patients benefit from therapy with chenodeoxycholic acid. Although the disease is clinically characterized by the concomitant presence of tendon xanthomas, juvenile cataracts and progressive neurological impairment, clinical features may vary greatly. Neuroradiological studies have suggested that the bilateral abnormality of the dentate nuclei could be typical of this disease. However, this finding has been seen inconsistently on conventional MRI. The dynamic of the CNS pathology in CTX is complex, and whether demyelination or axonopathy has primary importance in the pathogenesis of CTX pathology is not known. To clarify both neuroradiological and pathological issues, we performed combined brain MRI and spectroscopy examinations on 12 CTX patients. On conventional MRIs, bilateral hyperintensities of the dentate nuclei were clearly seen in nine out of 12 patients on T(2) -weighted MRIs, but were evident in all patients using a FLAIR sequence. On proton magnetic resonance (MR) spectroscopy, significant decreases in N: -acetylaspartate resonance intensities (P: <0.0001) and increases in lactate MR signals (P<0.05) were found in the group of CTX patients in large volumes of interest localized above the lateral brain ventricles and in the cerebellar hemispheres. Cerebral values of N -acetylaspartate resonance intensities showed a close correlation with patients' disability (Spearman rank correlation = -0.78, P<0.005). These results suggest that MR abnormalities in the dentate nuclei may be evident consistently in patients with CTX. Proton MR spectroscopy data demonstrated widespread axonal damage (as shown by the decrease in N -acetylaspartate) and diffuse brain mitochondrial dysfunction (as shown by the increase in brain parenchymal lactate) in patients with CTX. The close correlation seen between values of the putative axonal marker N-acetylaspartate and patients' disability scores suggests that proton MR spectroscopy can provide a useful measure of disease outcome in CTX.

Update on genetic disorders affecting white matter

The classification of diseases affecting white matter has changed dramatically with the use of magnetic resonance imaging. Classical leukodystrophies, such as metachromatic leukodystrophy and Krabbe's disease, account for only a small number of inherited diseases that affect white matter. Magnetic resonance imaging has clarified genetic disorders that result in white matter changes or leukoencephalopathies. The term leukoencephalopathy is used to reflect the broader number of diseases that may cause as either primary or secondary changes in myelin development. This review attempts to categorize white matter disorders into classes such as lipid, myelin protein, organic acids, and defects in energy metabolism, in addition to other causes.