Enzyme replacement therapy improves peripheral nerve and sweat function in Fabry disease

Fabry disease is an X-linked disorder caused by a deficiency of lysosomal alpha-galactosidase A resulting in accumulation of alpha-D-galatosyl conjugated glycosphingolipids. Clinical manifestations include a small-fiber neuropathy associated with debilitating pain and hypohidrosis. We report the effect of a 3-year open-label extension of a previously reported 6-month placebo-controlled enzyme replacement therapy (ERT) trial in which 26 hemizygous patients with Fabry disease received 0.2 mg/kg of alpha-galactosidase A every 2 weeks. The effect of ERT on neuropathic pain scores while off pain medications, quantitative sensory testing, quantitative sudomotor axon reflex test (QSART), and thermoregulatory sweat test (TST) is reported. In the patients who crossed-over from placebo to ERT (n = 10), mean pain-at-its-worst scores on a 0-10 scale decreased (from 6.9 to 4.5). There was a significant reduction in the threshold for cold and warm sensation in the foot. At the 3-year time-point, pre-ERT sweat excretion in 17 Fabry patients was 0.24 +/- 0.33 microl/mm(2) vs. 1.05 +/- 0.81 in concurrent controls (n = 38). Sweat function improved 24-72 h post-enzyme infusion (0.57 +/- 0.71 microl/mm(2)) and normalized in four anhidrotic patients. TST confirmed the QSART results. We conclude that prolonged ERT in Fabry disease leads to a modest but significant improvement in the clinical manifestations of the small-fiber neuropathy associated with this disorder. QSART may be useful to further optimize the dose and frequency of ERT.     

A novel mutation of α-galactosidase A gene causes Fabry disease mimicking primary erythromelalgia in a Chinese family

Purpose: Fabry disease is an X-linked genetic disorder caused by the mutations of α-galactosidase A (GLA, MIM 300644) gene presenting with various clinical symptoms including small-fiber peripheral neuropathy and limb burning pain. Here, we reported a Chinese pedigree with the initial diagnosis of primary erythromelalgia in an autosomal dominant (AD)-inherited pattern. Methods: Mutation analysis of SCN9A and GLA genes by direct sequencing and functional analysis of a novel mutation of GLA in cells were performed. Results: Our data did not show any pathological mutations in SCN9A gene; however, a novel missense mutation c.139T>C (p.W47R) of GLA was identified in a male proband as well as two female carriers in this family. Enzyme assay of α-galactosidase A activity showed deficient enzyme activity in male patients and female carriers, further confirming the diagnosis of Fabry disease. Finally, a functional analysis indicated that the replacement of the 47th amino acid tryptophan (W47) with arginine (W47R) or glycine (W47G) led to reduced activity of α-galactosidase A in 293T cells. Therefore, these findings demonstrated that the novel mutation p.W47R of GLA is the cause of Fabry disease. Conclusions: Because Fabry disease and primary erythromelalgia share similar symptoms, it is a good strategy for clinical physicians to perform genetic mutation screenings on both SCN9A and GLA genes in those patients with limb burning pain but without a clear inheritant pattern.     

Idiopathic Small Fiber Neuropathy: Phenotype,Etiologies, and the Search for Fabry Disease

Background and Purpose

The etiology of small fiber neuropathy (SFN) often remains unclear. Since SFN may be the only symptom of late-onset Fabry disease, it may be underdiagnosed in patients with idiopathic polyneuropathy. We aimed to uncover the etiological causes of seemingly idiopathic SFN by applying a focused investigatory procedure, to describe the clinical phenotype of true idiopathic SFN, and to elucidate the possible prevalence of late-onset Fabry disease in these patients.

Methods

Forty-seven adults younger than 60 years with seemingly idiopathic pure or predominantly small fiber sensory neuropathy underwent a standardized focused etiological and clinical investigation. The patients deemed to have true idiopathic SFN underwent genetic analysis of the alpha-galactosidase A gene (GLA) that encodes the enzyme alpha-galactosidase A (Fabry disease).

Results

The following etiologies were identified in 12 patients: impaired glucose tolerance (58.3%), diabetes mellitus (16.6%), alcohol abuse (8.3%), mitochondrial disease (8.3%), and hereditary neuropathy (8.3%). Genetic alterations of unknown clinical significance in GLA were detected in 6 of the 29 patients with true idiopathic SFN, but this rate did not differ significantly from that in healthy controls (n=203). None of the patients with genetic alterations in GLA had significant biochemical abnormalities simultaneously in blood, urine, and skin tissue.

Conclusions

A focused investigation may aid in uncovering further etiological factors in patients with seemingly idiopathic SFN, such as impaired glucose tolerance. However, idiopathic SFN in young to middle-aged Swedish patients does not seem to be due to late-onset Fabry disease.     

Enzyme replacement therapy and intraepidermal innervation density in Fabry disease

We prospectively evaluated the effect of enzyme replacement therapy (ERT) on the intraepidermal nerve fiber density (IENFD) and thermal threshold in patients with Fabry disease, an X-linked disorder associated with a painful small-fiber neuropathy and decreased linear IENFD in a length-dependent pattern. Twenty-five hemizygous male patients with Fabry disease were enrolled in a 6-month, randomized, placebo-controlled ERT trial of 0.2 mg/kg of alpha-galactosidase A (agalsidase-alfa) every 2 weeks followed by an additional 12 months of open-label ERT for both populations. IENFD and thermal threshold were measured in the distal thigh at baseline, 6 months, and 18 months from initiation of the trial. We found no significant difference in IENFD between the treatment groups at 6 months. After an additional year of ERT, there was a significant reduction in IENFD in the patient group as a whole, attributable to the declining glomerular filtration rate. Thermal thresholds remained unchanged. We conclude that epidermal nerve fiber regeneration, as measured in the distal thigh, does not occur in this patient population after 12-18 months of ERT.     

Neurological features of Fabry disease: clinical, pathophysiological aspects and therapy

Fabry disease is a multisystem, X-linked, lysosomal storage disorder caused by a mutation in the GLA gene on chromosome Xq22 resulting in alpha-galactosidase A enzyme (α-Gal A) deficiency. Neurological manifestations other than cerebrovascular accidents include small fibre neuropathy and dysautonomic disorders, which may be the presenting clinical features in a proportion of patients. An atypical disease onset may be misdiagnosed until the emergence of a more typical clinical picture, characterized by chronic renal and cardiac failure. Thus, neurologists should consider Fabry disease in differential diagnosis and provide an appropriate diagnostic work up. This review focuses on central and peripheral nervous system involving available diagnostic tools and diagnostic work up in Fabry disease. It also covers the most recent evidence regarding enzyme replacement therapy.     

Phenotypical characterization of α-galactosidase A gene mutations identified in a large Fabry disease screening program in stroke in the young

Objective

In the Belgian Fabry Study (BeFaS), the prevalence of Fabry disease was assessed in 1000 young patients presenting with stroke, unexplained white matter lesions or vertebrobasilar dolichoectasia. The results of the BeFaS suggested that Fabry disease may play a role in up to 1% of young patients presenting with cerebrovascular disease. However, the clinical relevance was unclear in all cases. We report on detailed phenotyping in subjects identified with α-galactosidase A (α-Gal A) enzyme deficiency or GLA mutations identified in the BeFaS (n = 10), and on the results of family screening in this population.

Methods

Family screening was performed to identify additional mutation carriers. Biochemical and/or clinical evaluation of all subjects (BeFaS index patients and relatives carrying a GLA mutation) was performed.

Results

Genetic family screening revealed 18 additional GLA mutation carriers. Bloodspot α-Gal A enzyme activity was normal in all GLA mutation carriers, even in 2 males with the p.A143T mutation. Plasma Gb3 and lyso-Gb3 levels were normal in all subjects. Elevated Gb3 in urine was detected in 2 subjects. Some classic clinical signs of Fabry disease, like angiokeratoma or cornea verticillata, could not be detected in our population. Cardiac symptoms of Fabry disease were found in 6 out of 10 p.A143T carriers. No signs of cerebrovascular disease were found in the relatives with a GLA mutation.

Conclusions

We could not identify mutations causing the classical clinical phenotype of Fabry disease in our cerebrovascular disease population. Enzyme activity analysis in bloodspots and plasma may fail to identify late-onset variants of Fabry disease. We recommend genetic testing when an atypical, late-onset variant of Fabry disease is suspected in a male cerebrovascular disease patient. However, this may lead to the identification of non-disease causing or controversial genetic variants.     

Neurophysiological, behavioral and morphological abnormalities in the Fabry knockout mice

Fabry disease (OMIM 301500) is a rare X-linked recessive disorder caused by mutations in the alpha-galactosidase gene (GLA). Loss of alpha-galactosidase (alpha-Gal) activity leads to the abnormal accumulation of glycosphingolipids in lysosomes predominantly of vascular endothelial cells. Clinically the disorder presents with angiokeratomas, clouding of the cornea, and renal, cardiac, and cerebrovascular complications. In addition, there is an increased incidence of neuropathic pain in Fabry patients. In this study, we investigated the implications of loss of alpha-galactosidase A activity on sensorimotor function and peripheral nervous system. Similar to the described in Fabry disease patients, the sensorimotor assessment of Fabry mice revealed diminished locomotor activity and warm hypoalgesia as assessed in the hot-plate. Moreover Fabry mice displayed alterations both in balance and co-ordination. By histological analysis, the cyto-architecture of Fabry mice sciatic nerves showed an increase in mean cross-sectional area accompanied by a decrease in the density of non-myelinated fibers as well as a trend for a decreased number of small myelinated fibers, a well established feature of Fabry disease. A relative preservation of large myelinated fibers and nerve conduction velocity measurements was observed. Our findings demonstrate for the first time that Fabry knockout mice have Gb3 accumulation in the peripheral nervous system, alterations in sensorimotor function, hypoalgesia and no impairment of motor nerve conduction.     

Adult polyglucosan body disease in a patient originally diagnosed with Fabry’s disease

Adult polyglucosan body disease is a rare autosomal recessive disease, caused by glycogen branching enzyme gene mutations, characterised by urinary dysfunction, spastic paraplegia with vibration sense loss, peripheral neuropathy, and cognitive impairment. Fabry’s disease is an X-linked lysosomal storage disorder caused by α-galactosidase A gene mutations; neurological manifestations include cerebrovascular accidents, small-fibre neuropathy and autonomic dysfunction. Here, we report the case of a 44-year-old Sicilian male with stroke-like episodes, hypohidrosis and mild proteinuria, which led to the diagnosis of Fabry’s disease after a hemizygous mutation (p.Ala143Thr) in α-galactosidase A gene was detected. Subsequently, he developed progressive walking difficulties and dementia, which were considered atypical for Fabry’s disease. Therefore, we performed additional investigations that eventually led to the diagnosis of adult polyglucosan body disease caused by two novel missense mutations (p.Asp413His and p.Gly534Val) in the glycogen branching enzyme gene. Recently, the pathogenic role of the p.Ala143Thr mutation in causing Fabry’s disease has been questioned. This case underlines the importance of performing further investigations when facing with atypical features even in the presence of a genetic diagnosis of a rare disease.     

Middelheim Fabry Study (MiFaS): a retrospective Belgian study on the prevalence of Fabry disease in young patients with cryptogenic stroke

OBJECTIVE: To assess the prevalence of Fabry disease in young patients with cryptogenic stroke. PATIENTS AND METHODS: We retrospectively assessed the prevalence of Fabry disease in patients aged 16-60 years that were admitted to ZNA Middelheim Hospital from January 1, 2000 to December 31, 2004 for cryptogenic stroke. We screened for Fabry disease by measurement of alpha-galactosidase A and beta-glucuronidase activity on blood spot. In all patients with abnormal enzymatic activity and in all female patients with low normal values, genetic sequencing of the alpha-GAL-gene was performed. RESULTS: In a population of 103 young patients with cryptogenic stroke that met the in- and exclusion criteria, we were unable to identify any patient with Fabry disease. CONCLUSION: Based on the results of alpha-galactosidase A and beta-glucuronidase activity, genetic sequencing and the low prevalence of clinical signs and symptoms of Fabry disease in this population, we believe that the true prevalence of Fabry disease in patients with cryptogenic stroke may be less than currently accepted in literature.     

Fasciculations and cramps: how benign? Report of four cases progressing to ALS

Clinical diagnosis of amyotrophic lateral sclerosis (ALS) in patients presenting with cramps and fasciculations may not be evident at the first consultation. Sequential reviews, clinical and neurophysiological, form an important part of clinical practice in such cases. Recent attempts to delineate a more benign group with cramps and fasciculations have lacked information on the long term profile, both clinical and neurophysiological. Four patients who were initially diagnosed as suffering from benign cramps and fasciculations, but who subsequently progressed to ALS, are described. We propose that a diagnosis of benign cramps and fasciculations should not be considered secure without a minimum follow up of 4–5 years.     

Motor Axonal Neuropathy During Treatment With Simvastatin

Simvastatin is a cholesterol-lowering drug that acts by inhibiting hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in cholesterol synthesis. Abnormal laboratory findings include transient increases in serum creatine kinase (CK) due to a myopathic syndrome. Rarely, neurological side effects include axonal sensory-motor peripheral neuropathy, characterized in some cases by a prevalent motor involvement accompanied by subclinical sensory damage. We report a case of purely motor axonal neuropathy associated with simvastatin. A 72-year-old woman, after five years of treatment with simvastatin, developed progressive weakness, cramps and fasciculations mainly involving proximal muscles in the lower limbs, though without sensory symptoms or signs. Deep reflexes were lost in the lower limbs. There was no sign of upper motor-neuron involvement. CK was elevated (up to 2000 U/l). EMG showed marked neurogenic damage with fibrillations and fasciculations in the lower limbs. ENG showed motor fiber loss within the lower limb nerves without involvement of sensory fibers. CSF examination was normal. Deltoid muscle biopsy showed neurogenic changes and some ragged-red fibers. One year after simvastatin withdrawal the patient's state of weakness improved and the cramps resolved. The CK level dropped to 700 U/l.     

Progressive arm weakness and tonic hand spasm from multifocal motor neuropathy in the brachial plexus

A 50-year-old waitress presented with a 10-year history of progressive weakness in her right arm without atrophy and with tonic hand spasms suggesting a central motor disorder. Electromyography, however, disclosed chronic neurogenic changes including fasciculations and atypical cramps. Isolated motor conduction block in the right brachial plexus suggested a variant of multifocal motor neuropathy. Strength recovered and cramps disappeared after intravenous immunoglobulins. Motor neuropathies may thus manifest with features of central motor disorders.     

Cutaneous silent periods in patients with Fabry disease

We assessed the cutaneous silent period (CSP) in 24 patients with Fabry disease with small-fiber sensory neuropathy and 12 normal subjects to test the hypothesis that small-diameter afferents are responsible for producing the CSP. Sensory nerve conduction studies and quantitative sensory testing for cold and vibration detection thresholds were also measured. Overall, Fabry patients had impaired thermal, but not vibration, detection thresholds, with greatest impairment in the feet. In the upper extremity, CSP latencies, duration, and suppression of electromyographic activity (EMG) did not differ. In the lower extremity, patients had reduced suppression of EMG during the CSP compared to normal controls. CSP durations exhibited a bimodal distribution in patients, including a subset of seven patients with durations shorter than all controls. This subset had profound loss of thermal sensation in the feet, but this was also true of some patients who had normal CSPs. Patients with shortened CSPs had modestly elevated vibration thresholds and reduced sensory potentials in comparison to patients with normal CSPs. Reduced CSPs in Fabry patients are associated with, but not entirely explained by, the severity of small-fiber neuropathy as measured by quantitative sensory testing. The possibility that large-diameter fibers provide a minor contribution to producing the CSP should be considered.     

Fabry disease: detection of 13-bp deletion in alpha-galactosidase A gene and its application to gene diagnosis of heterozygotes.

Polymerase chain reaction amplification of reverse-transcribed messenger RNA from a patient with Fabry disease revealed a 13-base pair deletion in the 5' region (exon 1) of alpha-galactosidase A complementary DNA. This gene rearrangement was not detected by Southern or Northern analysis. Short direct repeats were present around the breakpoints, and considered to be of pathogenetic significance. Gene diagnosis of the mother and a female cousin was successfully achieved by polymerase chain reaction amplification of genomic DNA; the former as a Fabry disease heterozygote and the latter as a normal homozygote.     

From benign fasciculations and cramps to motor neuron disease

Fasciculations and cramps may occur in motor neuron disease or as part of a more benign syndrome. A man with apparently benign fasciculations and cramps for 4 years developed progressive muscle weakness and wasting. Such a previously undocumented evolution of benign fasciculations and cramps to motor neuron disease may further implicate anterior horn cell dysfunction in the pathogenesis of muscle fasciculation-cramp syndromes.     

Screening for Fabry's disease in young patients with ischemic stroke in a Chinese population

Purpose: Fabry disease is an X-linked lysosomal storage disorder frequently associated with cerebrovascular disease. Data regarding Fabry disease and ischemic stroke has been lacking in China. In this study, we investigated the prevalence of Fabry disease and the distribution of the alpha-galactosidase A (α-GalA) gene – GLA mutations in young stroke patients in the Chinese population and its association with stroke subtypes. Methods : A total of 357 ischemic stroke patients admitted to Xuanwu Hospital of Capital Medical University, aged 18–55 years old, including 293 patients with cerebral infarction and 64 patients with transient ischemic attack, were enrolled in this study. Mutations in the GLA gene were screened by Sanger sequencing. Enzyme levels were measured to further confirm the disease in patients with the gene mutation. The mutation frequency was compared among different stroke subtypes and further compared with the control group individually. Results : No pathogenic mutations in the coding regions of the GLA gene were identified in this group of patients and thus no Fabry disease was found in our study. However, the frequency of an intronic polymorphism c.-10C>T was significantly different among different Trial of Org 10172 in Acute Stroke Treatment subtypes (p < 0.01). The frequency of the c.-10C>T polymorphism in patients with stroke due to other causes and undetermined causes was much higher than that in the control group (OR = 3.18, 95% CI: 1.29–7.83, p < 0.01). Conclusions: Fabry disease is a rare disease, and it will not benefit to screen all stroke patients. In addition, our results suggested that the c.-10C>T polymorphism may be a risk factor for ischemic stroke of other and undetermined causes. Further study is required to confirm our findings.     

A novel nonsense mutation (Q352X) in the mitochondrial cytochrome b gene associated with a combined deficiency of complexes I and III.

We identified a novel mitochondrial cytochrome b mutation in a patient with progressive exercise intolerance, muscle cramps and lactic acidosis. A marked reduction of the enzymatic activities of respiratory chain complexes I and III was found in muscle biopsy. The mutation was a heteroplasmic C15800T transition, determining a stop-codon at amino acid position 352 (Q352X). Mutant mtDNA was approximately 45% of total genomes in muscle, while it was absent in all of the other examined tissues of the patient and in lymphocytes of the patient's mother. Clinical presentation and laboratory findings strongly support the hypothesis that this mutation is the primary cause of the disease in our patient.     

Skin denervation in vasculitic neuropathy

BACKGROUND: Skin denervation in vasculitic neuropathy has rarely been documented despite frequent manifestations of small-fiber neuropathy including reduced sensitivity and neuropathic pain. Recently, skin biopsy has been established as a new approach to diagnose small-fiber sensory neuropathy. OBJECTIVES: To investigate the pathologic features of cutaneous nerves and to evaluate inflammatory vasculopathy in the skin of patients with vasculitis. DESIGN: Case series. SETTING: National Taiwan University Hospital, Taipei.Patients Six patients with vasculitic neuropathy. INTERVENTIONS: Patients had 3-mm punch biopsy specimens taken from the distal part of the leg (without active vasculitic lesions) and a sural nerve biopsy specimen was taken in addition to detailed neurologic examinations, laboratory investigations, and nerve conduction studies. MAIN OUTCOME MEASURES: Results of nerve conduction studies, epidermal nerve fiber density studies, and immunohistochemistry. RESULTS: All 6 patients had combined large- and small-nerve-fiber involvement on the neurologic examinations. Nerve conduction studies showed a pattern of axonal neuropathy or mononeuropathy multiplex. Epidermal nerve fiber densities were significantly reduced in the skin of all patients, consistent with concomitant small-fiber neuropathies. Perivascular infiltration by T cells and macrophages was demonstrated by immunohistochemistry. All patients experienced neurologic improvement in muscle strength and alleviation of sensory symptoms after immunotherapy with corticosteroids, plasma exchange, or cyclophosphamide. CONCLUSIONS: Small-diameter sensory nerves are affected in vasculitis in addition to the well-known effect of vasculitis on large-diameter nerves. Significant inflammatory vasculopathy is present in the skin despite the absence of clinically active vasculitic lesions.     

Neurological aspects of Fabry's disease

Fabry disease is a rare X-linked disorder caused by deficient activity of the lysosomal enzyme alpha-galactosidase A. Progressive accumulation in lysosomes of the undegraded glycosphingolipids leads to a multi-system disease with dermatological, ocular, renal, cardiac, and neurological manifestations. Peripheral nerve involvement, neuropathic pain and chronic acroparesthesiae, are frequent and early-onset signs revealing the disease. They are due to the involvement of small nerve fiber, thus explaining the normality of electroneuromyography. Cochleo-vestibular and autonomic nervous system involvement is frequent. Besides rare aseptic meningitis, central nervous system involvement is essentially represented by cerebrovascular events (stroke, transient ischemic attack). Affecting essentially the posterior circulation, their etiologies have to be clarified: progressive stenosis of small vessels with globotriasocylceramide deposits, arterial remodeling, endothelial dysfunction, pro-thrombotic state, cerebral hypoperfusion consecutive to dysautonaumy, cardiac embolism. MRI shows numerous silent lesions, increasing with age, mainly in small perforant arteries (periventricular white matter, brainstem, cerebellum, basal ganglia). Pulvinar calcifications, due to an increase in cerebral hyperperfusion, could be specific of Fabry disease. Positon tomography analysis shows a reduced cerebral flow velocity and impaired cerebral autoregulation, secondary to the glycosphingolipid storage in vascular endothelial cells. Enzyme replacement therapy has to be carefully monitored.     

Motor neuron disease following generalized fasciculations and cramps

We report a case of motor neuron disease in which fasciculations and cramps progressed generally before the development of muscle wasting. After involvement of the upper and lower motor neurons became clinically manifest, widespread fasciculations and cramps persisted and accompanied pseudotetany. The present case suggests that spinal cord pathology of motor neuron disease can cause the abnormal excitability of the motor neurons, resulting in the development of generalized fasciculations and cramps.