Pathophysiology and assessment of neuropathic pain in Fabry disease

Molecular Pathogenesis of Central and Peripheral Nervous System Complications in Anderson-Fabry Disease

Fabry disease (FD) is a recessive monogenic disease linked to chromosome X due to more than two hundred mutations in the alfa-galactosidase A (GLA) gene. Modifications of the GLA gene may cause the progressive accumulation of globotriaosylceramide (Gb3) and its deacylated form, globotriasylsphingosine (lyso-Gb3), in lysosomes of several types of cells of the heart, kidneys, skin, eyes, peripheral and central nervous system (not clearly and fully demonstrated), and gut with different and pleiotropic clinical symptoms. Among the main symptoms are acroparesthesias and pain crisis (involving the peripheral nervous system), hypohidrosis, abdominal pain, gut motility abnormalities (involving the autonomic system), and finally, cerebrovascular ischemic events due to macrovascular involvement (TIA and stroke) and lacunar strokes and white matter abnormalities due to a small vessel disease (SVS). Gb3 lysosomal accumulation causes cytoplasmatic disruption and subsequent cell death. Additional consequences of Gb3 deposits are inflammatory processes, abnormalities of leukocyte function, and impaired trafficking of some types of immune cells, including lymphocytes, monocytes, CD8+ cells, B cells, and dendritic cells. The involvement of inflammation in AFD pathogenesis conflicts with the reported poor correlation between CRP levels as an inflammation marker and clinical scores such as the Mainz Severity Score Index (MSSI). Also, some authors have suggested an autoimmune reaction is involved in the disease's pathogenetic mechanism after the α-galactosidase A deficiency. Some studies have reported a high degree of neuronal apoptosis inhibiting protein as a critical anti-apoptotic mediator in children with Fabry disease compared to healthy controls. Notably, this apoptotic upregulation did not change after treatment with enzymatic replacement therapy (ERT), with a further upregulation of the apoptosis-inducing factor after ERT started. Gb3-accumulation has been reported to increase the degree of oxidative stress indexes and the production of reactive oxygen species (ROS). Lipids and proteins have been reported as oxidized and not functioning. Thus, neurological complications are linked to different pathogenetic molecular mechanisms. Progressive accumulation of Gb3 represents a possible pathogenetic event of peripheral nerve involvement. In contrast, central nervous system participation in the clinical setting of cerebrovascular ischemic events seems to be due to the epitheliopathy of Anderson-Fabry disease with lacunar lesions and white matter hyperintensities (WMHs). In this review manuscript, we revised molecular mechanisms of peripheral and central neurological complications of Anderson-Fabry Disease. The management of Fabry disease may be improved by the identification of biomarkers that reflect the clinical course, severity, and progression of the disease. Intensive research on biomarkers has been conducted over the years to detect novel markers that may potentially be used in clinical practice as a screening tool, in the context of the diagnostic process and as an indicator of response to treatment. Recent proteomic or metabolomic studies are in progress, investigating plasma proteome profiles in Fabry patients: these assessments may be useful to characterize the molecular pathology of the disease, improve the diagnostic process, and monitor the response to treatment.

Assessment of small fiber neuropathy in patients carrying the non-classical Fabry variant p.D313Y

INTRODUCTION

The pathophysiological significance of the Fabry-related, non-classical variant p.D313Y still remains to be solved. This study assesses the involvement of the peripheral nervous system with respect to small fiber neuropathy and neuropathic pain in female patients carrying p.D313Y.

METHODS

This study examined nine females carrying the Fabry-related p.D313Y variant by obtaining skin punch biopsies above the right lateral malleolus. Intraepidermal nerve fiber density was determined for each patient and compared to reference values matched for the patient's decade of life and sex. Moreover, each patient was characterized by a detailed neurological examination and by pain assessment via questionnaire.

RESULTS

Compared to sex-matched lower fifth percentile reference values per decade, intraepidermal nerve fiber density was decreased in seven out of nine patients. Four patients reported acral paresthesias and neuropathic pain with an average visual analogue scale score of 7 out of 10 points. Two patients experienced acute pain crises. Six out of seven patients diagnosed with small fiber neuropathy had a their medical history of hypo- and/or hyperhidrosis.

DISCUSSION

The diagnosis of small fiber neuropathy was made in seven out of nine females carrying the non-classical variant p.D313Y. Moreover, neuropathic pain and symptoms indicative of autonomic nervous system dysfunction seem to be common findings that may be of clinical significance and may warrant therapeutic intervention.

Altered globotriaosylceramide accumulation and mucosal neuronal fiber density in the colon of the Fabry disease mouse model

BACKGROUND

Fabry disease (FD) is a hereditary X-linked metabolic storage disorder characterized by deficient or absent lysosomal α-galactosidase A (α-Gal A) activity. This deficiency causes progressive accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3), in nearly all organ systems. Gastrointestinal (GI) symptoms can be very debilitating and are among the most frequent and earliest of the disease. As the pathophysiology of these symptoms is poorly understood, we carried out a morphological and molecular characterization of the GI tract in α-Gal A knockout mice colon in order to reveal the underlying mechanisms.

METHODS

Here, we performed the first morphological and biomolecular characterization of the colon wall structure in the GI tract of the α-Gal A knock-out mouse (α-Gal A -/0), a murine model of FD.

KEY RESULTS

Our data show a greater thickness of the gastrointestinal wall in α-Gal A (-/0) mice due to enlarged myenteric plexus' ganglia. This change is paralleled by a marked Gb3 accumulation in the gastrointestinal wall and a decreased and scattered pattern of mucosal nerve fibers.

CONCLUSIONS AND INFERENCES

The observed alterations are likely to be a leading cause of gut motor dysfunctions experienced by FD patients and imply that the α-Gal A (-/0) male mouse represents a reliable model for translational studies on enteropathic pain and GI symptoms in FD.

Human dorsal root ganglion in vivo morphometry and perfusion in Fabry painful neuropathy

Objective:

To evaluate functional and morphometric magnetic resonance neurography of the dorsal root ganglion and peripheral nerve segments in patients with Fabry painful neuropathy.

Methods:

In this prospective study, the lumbosacral dorsal root ganglia and proximal peripheral nerve segments of the lower extremity were examined in 11 male patients with Fabry disease by a standardized 3T magnetic resonance neurography protocol. Volumes of L3 to S2 dorsal root ganglia, perfusion parameters of L5-S1 dorsal root ganglia and the spinal nerve L5, and the cross-sectional area of the proximal sciatic nerve were compared to healthy controls.

Results:

Dorsal root ganglia of patients with Fabry disease were symmetrically enlarged by 78% (L3), 94% (L4), 122% (L5), 115% (S1), and 119% (S2) (p < 0.001). In addition, permeability of the blood-tissue interface was decreased by 53% (p < 0.001). This finding was most pronounced in the peripheral zone of the dorsal root ganglion containing the cell bodies of the primary sensory neurons (p < 0.001). Spinal nerve permeability showed no difference between patients with Fabry disease and controls (p = 0.7). The sciatic nerve of patients with Fabry disease at the thigh level showed an increase in cross-sectional area by 48% (p < 0.001).

Conclusions:

Patients with Fabry disease have severely enlarged dorsal root ganglia with dysfunctional perfusion. This may be due to glycolipid accumulation in the dorsal root ganglia mediating direct neurotoxic effects and decreased neuronal blood supply. These alterations were less pronounced in peripheral nerve segments. Thus, the dorsal root ganglion might play a key pathophysiologic role in the development of neuropathy and pain in Fabry disease.

Neuro-Otological and Peripheral Nerve Involvement in Fabry Disease

Fabry disease (FD) is an X-linked lysosomal storage disease, with multisystemic glycosphingolipids deposits. Neuro-otological involvement leading to hearing loss and vestibular dysfunctions has been described, but there is limited information about the frequency, site of lesion, or the relationship with peripheral neuropathy. The aim was to evaluate the presence of auditory and vestibular symptoms, and assess neurophysiological involvement of the VIII cranial nerve, correlating these findings with clinical and neurophysiological features of peripheral neuropathy. We studied 36 patients with FD with a complete neurological and neuro-otological evaluation including nerve conduction studies, quantitative sensory testing (to evaluate small fiber by warm and cold threshold detection and cold and heat pain), vestibular evoked myogenic potentials, videonistagmography, audiometry and brainstem auditory evoked potentials. Neuro-otologic symptoms included hearing loss (22.2%), vertigo (27.8%) or both (25%). An involvement of either cochlear or vestibular function was identified in most patients (75%). In 70% of our patients the involvement of both cochlear and vestibular function could not be explained by a neural or vascular mechanism. Small fiber neuropathy was identified in 77.7%. There were no significant associations between neuro-otological and QST abnormalities. Neuro-otologic involvement is frequent and most likely under-recognized in patients with FD. It lacks a specific neural or vascular pattern, suggesting multi-systemic, end organ damage. Small fiber neuropathy is an earlier manifestation of FD, but there is no correlation between the development of neuropathy and neuro-otological abnormalities.

Skin globotriaosylceramide 3 deposits are specific to Fabry disease with classical mutations and associated with small fibre neuropathy

Background

Fabry Disease (FD) is characterized by globotriaosylceramide-3 (Gb3) accumulation in several tissues and a small fibre neuropathy (SFN), however the underlying mechanisms are poorly known. This study aimed to: 1) ascertain the presence of Gb3 deposits in skin samples, by an immunofluorescence method collected from FD patients with classical GLA mutations or late-onset FD variants or GLA polymorphisms; 2) correlate skin GB3 deposits with skin innervation.

Methods

we studied 52 genetically-defined FD patients (32 with classical GLA mutations and 20 with late-onset variants or GLA polymorphisms), 15 patients with SFN associated with a specific cause and 22 healthy controls. Subjects underwent skin biopsy to evaluate Gb3 deposits and epi-dermal innervation.

Results

Skin Gb3 deposits were found in all FD patients with classical GLA mutations but never in FD patients with late-onset variants or GLA polymorphisms or in patients with SFN and healthy controls. Abnormal deposits were found inside different skin structures but never inside axons. FD patients with GB3 deposits showed lower skin innervation than FD patients with late-onset variants or polymorphisms.

Conclusions

1) Skin Gb3 deposits are specific to FD patients with classical GLA mutations; 2) Gb3 deposits were associated with lower skin innervation but they were not found inside axons, suggesting an indirect damage on peripheral small fibre innervation.

[The neurological manifestations of Fabry disease. A review]

Fabry disease (Anderson-Fabry disease) is an X-linked recessive lysosomal storage disorder resulting from deficient activity of lysosomal hydrolase, alpha-galactosidase A (alpha-Gal A), which leads to progressive accumulation of globotriaosylceramide (Gb3) in various cells, predominantly endothelial and vascular smooth muscle cells, with clinical manifestations affecting major organs including the central nervous system. Manifestations of Fabry disease include progressive renal and cardiac insufficiency, neuropathic pain, stroke and cerebral disease, skin and gastrointestinal symptoms. Clinical onset usually occurs in childhood, but many severe patients are diagnosed in adulthood. Females may be severely affected as males and both may die prematurely due to stroke, heart disease and renal failure. Early recognition of symptoms, enzyme activity levels, concentration of Gb3 levels in the blood, urine and skin biopsies, as well as genetic testing (GLA gene) enable establishment of early diagnosis and therapeutic intervention with enzyme replacement therapy. Enzyme replacement therapy can stabilize or reduce the progression of the disease. Early therapy may prevent complications of the disease.

Development of a model system for neuronal dysfunction in Fabry disease

Fabry disease is a glycosphingolipid storage disorder that is caused by a genetic deficiency of the enzyme alpha-galactosidase A (AGA, EC 3.2.1.22). It is a multisystem disease that affects the vascular, cardiac, renal, and nervous systems. One of the hallmarks of this disorder is neuropathic pain and sympathetic and parasympathetic nervous dysfunction. The exact mechanism by which changes in AGA activity result in change in neuronal function is not clear, partly due to of a lack of relevant model systems. In this study, we report the development of an in vitro model system to study neuronal dysfunction in Fabry disease by using short-hairpin RNA to create a stable knock-down of AGA in the human cholinergic neuronal cell line, LA-N-2. We show that gene-silenced cells show specifically reduced AGA activity and store globotriaosylceramide. In gene-silenced cells, release of the neurotransmitter acetylcholine is significantly reduced, demonstrating that this model may be used to study specific neuronal functions such as neurotransmitter release in Fabry disease.

Increased expression of Trpv1 in peripheral terminals mediates thermal nociception in Fabry disease mouse model

Fabry disease is a X-linked lysosomal storage disorder caused by deficient function of the alpha-galactosidase A (α-GalA) enzyme. α-GalA deficiency leads to multisystemic clinical manifestations caused by the preferential accumulation of globotriaosylceramide (Gb3) in the endothelium and vascular smooth muscles. A hallmark symptom of Fabry disease patients is neuropathic pain that appears in the early stage of the disease as a result of peripheral small fiber damage. The α-GalA gene null mouse model (α-GalA(-/0)) has provided molecular evidence for the molecular alterations in small type-C nociceptors in Fabry disease that may underlie their hyperexcitability, although the specific mechanism remains elusive. Here, we have addressed this question and report that small type-C nociceptors from α-GalA(-/0) mice exhibit a significant increase in the expression and function of the TRPV1 channel, a thermoTRP channel implicated in painful heat sensation. Notably, male α-GalA(-/0) mice displayed a ≈2-fold higher heat sensitivity than wild-type animals, consistent with the augmented expression levels and activity of TRPV1 in α-GalA(-/0) nociceptors. Intriguingly, blockade of neuronal exocytosis with peptide DD04107, a process that inhibits among others the algesic membrane recruitment of TRPV1 channels in peptidergic nociceptors, virtually eliminated the enhanced heat nociception of α-GalA(-/0) mice. Together, these findings suggest that the augmented expression of TRPV1 in α-GalA(-/0) nociceptors may underly at least in part their increased heat sensitivity, and imply that blockade of peripheral neuronal exocytosis may be a valuable pharmacological strategy to reduce pain in Fabry disease patients, increasing their quality of life.

Pain in Fabry Disease: Practical Recommendations for Diagnosis and Treatment

Aims

Patients with Fabry disease (FD) characteristically develop peripheral neuropathy at an early age, with pain being a crucial symptom of underlying pathology. However, the diagnosis of pain is challenging due to the heterogeneous and nonspecific symptoms. Practical guidance on the diagnosis and management of pain in FD is needed.

Methods

In 2014, experts met to discuss recent advances on this topic and update clinical guidance.

Results

Emerging disease‐specific tools, including FabryScan, Fabry‐specific Pediatric Health and Pain Questionnaire, and Würzburg Fabry Pain Questionnaire, and more general tools like the Total Symptom Score can aid diagnosis, characterization, and monitoring of pain in patients with FD. These tools can be complemented by more objective and quantifiable sensory testing. In male and female patients of any age, pain related to FD can be an early indication to start disease‐specific enzyme replacement therapy before potentially irreversible organ damage to the kidneys, heart, or brain occurs.

Conclusion

To improve treatment outcomes, pain should be diagnosed early in unrecognized or newly identified FD patients. Treatment should include: (a) enzyme replacement therapy controlling the progression of underlying pathology; (b) adjunctive, symptomatic pain management with analgesics for chronic neuropathic and acute nociceptive, and inflammatory or mixed pain; and (c) lifestyle modifications.

Pain management strategies for neuropathic pain in Fabry disease--a systematic review

Background

Neuropathic pain is one of the key features of (classical) Fabry disease (FD). No randomized clinical trials comparing effectiveness of different pain management strategies have been performed. This review aims to give an overview of existing pain management strategies.

Methods

PubMed and Embase were searched up to September 2014 for relevant articles on treatment of neuropathic pain in FD.

Results

Seven-hundred-thirty-one articles were identified of which 26 were included in the analysis. Studies reported on 55 individuals in total, with group-sizes ranging from 1 to 8. Carbamazepine appeared most beneficial: complete pain relief in 5/25, partial relief in 17/25, and no benefit in 3/25 patients. Phenytoin resulted in complete relief in 1/27, partial relief in 12/27 and no benefit in 6/27 patients. In 8 patients a significant reduction in the frequency of pain attacks was described. Gabapentin caused partial relief in 6/7 and no relief in 1/7 patients. Little evidence was reported for SSNRI’s or treatment combinations. Adverse-effects were reported in all treatment strategies.

Conclusions

Only for carbamazepine, phenytoin and gabapentin there is evidence of effectiveness in neuropathic pain due to FD, but comparison of effectiveness between these drugs is lacking. In routine clinical practice adverse-effects may discourage use of carbamazepine and phenytoin in favor of second-generation antiepileptic drugs, but this is currently not supported by clinical evidence. This review suffers greatly from incomplete outcome reports and a predominance of case reports, which emphasizes the need for robust clinical trials and observational cohort studies.

Fabry disease: a rare cause of neuropathic pain

Fabry disease is characterized by burning or shooting pains in hands and feet, which have a severe impact on the quality of life of patients. It is therefore of importance that Fabry patients receive adequate diagnosis, counseling, treatment and follow up. This review describes neuropathic pain in classical Fabry disease with the aim to help clinicians to recognize Fabry patients among patients presenting with chronic extremity pain. The diagnostic dilemmas in patients with neuropathic pain and a non-classical disease course are discussed, together with the available diagnostic modalities, pain medication options and the effect of enzyme replacement therapy on small fiber neuropathy.

Enzyme replacement therapy in two Japanese siblings with Fabry disease, and its effectiveness on angiokeratoma and neuropathic pain

Enzyme replacement therapy (ERT) for Fabry disease does not show a clear benefit in angiokeratoma. We describe two Japanese siblings with Fabry disease, who were diagnosed when angiokeratomas were found on the older sibling at the age of 13 years. Neither of the boys complained of pain, while both suffered from hypohidrosis. We evaluated the safety and efficacy of ERT with recombinant human agalsidase alfa (Replagal®, Dainippon-Sumitomo Pharma. Co., Osaka, Japan) in these siblings over a 5-year period. In both siblings, sweating was observed 3 months after the initiation of ERT, which motivated them to adhere to ERT. Pain sensation was regained after 12 to 36 months of ERT, followed by a decrease after 48 to 60 months. Angiokeratomas on the lateral side of the knee of the older sibling partially disappeared after 48 months of ERT. Although the height of both siblings at baseline was lower than the corresponding average age-related heights in the normal Japanese population, during ERT they were within, or close to, the average +1 standard deviation in the non-Fabry population. Their growth rate seemed to indicate catch-up growth. Other clinical symptoms were maintained at baseline levels. Immunoglobulin G anti-agalsidase alfa antibodies were not detected in both sibling during ERT, and no infusion-associated reaction was observed. The treatment was generally well tolerated. ERT was a safe and effective treatment for angiokeratoma and neuropathic pain for these two siblings with Fabry disease.

Mobilome and genetic modification of bifidobacteria

Until recently, proper development of molecular studies in Bifidobacterium species has been hampered by growth difficulties, because of their exigent nutritive requirements, oxygen sensitivity and lack of efficient genetic tools. These studies, however, are critical to uncover the cross-talk between bifidobacteria and their hosts' cells and to prove unequivocally the supposed beneficial effects provided through the endogenous bifidobacterial populations or after ingestion as probiotics. The genome sequencing projects of different bifidobacterial strains have provided a wealth of genetic data that will be of much help in deciphering the molecular basis of the physiological properties of bifidobacteria. To this end, the purposeful development of stable cloning and expression vectors based on robust replicons - either from temperate phages or resident plasmids - is still needed. This review addresses the current knowledge on the mobile genetic elements of bifidobacteria (prophages, plasmids and transposons) and summarises the different types of vectors already available, together with the transformation procedures for introducing DNA into the cells. It also covers recent molecular studies performed with such vectors and incipient results on the genetic modification of these organisms, establishing the basis that would allow the use of bifidobacteria for future biotechnological applications.

Small fiber neuropathy in Fabry disease

Previous studies have explicitly shown that small nerve fibers are affected in Fabry disease which is assumed to cause the severe neuropathic pain that patients may have from childhood on. Neuropathic pain and small fiber neuropathy characteristics have therefore been considered as appropriate study endpoints in studies on the efficacy of enzyme replacement therapy. However, the relationship between small fiber neuropathy characteristics and pain, as well as the course of small fiber neuropathy in Fabry disease is still uncertain. In this article a comprehensive overview of the existing literature on small nerve fiber function and structure and the relationship with pain, age and disease severity is presented supplemented with data from the Dutch Fabry cohort, with the aim to identify consensus as well as controversies and to propose a hypothesis on the evolution of neuropathy in Fabry disease.

Early nutritional environment: focus on health effects of microbiota and probiotics

Balanced maternal nutrition during pregnancy ensures both the growth and development of the foetus and the well-being of the mother. Recent evidence supports the programming theory, which envisages long-lasting effects on later risk of chronic life-style-related diseases by early nutrition. The increasing problem of overweight, affecting almost half of the female population in Western societies, sets off adverse programming effects in the offspring manifested in subsequent health effects. To combat this problem, new tools involving life-style modifications are being actively sought to increment the traditional approaches. Immunonutrition, the ability of nutrients to influence the activities of cells in the immune system, may be one answer in combating low-grade systemic inflammation, the key underlying determinant in the obesity epidemic. Further, microbial compounds possess immunomodulatory properties which may be utilised to improve immune responses in clinically meaningful ways. Aberrant microbiota compositions have been detected during critical periods when early programming occurs, including pregnancy and infancy. Such alterations may regulate the health of the infant and the risk of subsequent disease, as demonstrated by the divergence in gut microbiota composition between healthy and overweight individuals. It may thus be hypothesised that the composition of the gut microbiota could be used as a target for intervention. Probiotics interact with the mucosal immune system via the same pathways as commensal bacteria to influence both innate and adaptive immune responses. In consequence, interventions with immunomodulatory diets, including certain nutrients and probiotics, may be critical in coordinating the adaptive function necessary for the formation of tolerance and thus in the prevention of undesirable metabolic consequences.

Impact of growing up with Fabry disease on achievement of psychosocial milestones and quality of life

Little is known on the impact of growing up with Fabry disease (FD) on psychosocial development. Children with FD may suffer from severe recurrent pains in hands and feet, gastro-intestinal symptoms and heat intolerance. These symptoms may influence quality of life and may interfere with a normal psychosocial development. It is important to evaluate psychosocial outcomes of patients with FD into adulthood to be able to optimize support of children with FD. The current cross-sectional questionnaire study investigated psychosocial development and quality of life of 28 young adults with FD, aged 18-35 years (9 males, 19 females), using the Course of Life questionnaire and the Short Form-36 questionnaire for quality of life. The results were compared with an age-matched normative population. We found significant differences in the achievement of milestones in social development of male Fabry patients. The milestones that were affected were 'going out to bars' and 'participation in sports activities'. Other than that FD patients appear to be able to achieve a rather normal psychosocial development until adulthood. Quality of life was decreased in Fabry males in the domains of physical functioning and bodily pain and of general health perception in females.

Awareness of Fabry disease among rheumatologists--current status and perspectives

Fabry disease is an inherited disorder of lipid metabolism caused by deficient activity of the lysosomal enzyme α-galactosidase A. Burning peripheral pain with triggered crises of excruciating pain and gastrointestinal dysmotility point to Fabry small fiber neuropathy; angiokeratoma, corneal deposits, and hypohidrosis are other common early manifestations. Progressive dysfunction of the kidneys, heart, and/or brain develops in adulthood. Diagnosis is often delayed which is of great concern, as therapeutic outcomes with enzyme replacement therapy are generally more favorable in early stages of Fabry disease. Results of a survey among 360 rheumatologists and pediatricians clinically managing patients with rheumatologic conditions demonstrate that Fabry manifestations are generally poorly recognized and that awareness of appropriate diagnostic tests is low. To raise awareness about the musculoskeletal aspects of Fabry disease among rheumatologists, the International Musculoskeletal Working Group on Lysosomal Storage Disorders has reviewed the current knowledge. We propose a diagnostic algorithm with burning pain in hands and feet and triggered attacks of excruciating pain as keystones. Evidence of autonomic nerve dysfunction and simple temperature sensitivity testing can provide important diagnostic clues. Multi-systemic involvement should be explored by taking a detailed medical history, including family history, and performing a thorough physical examination and appropriate laboratory workup. Confirmatory tests include the α-Gal A enzyme activity assay (males) and genetic testing (females). We propose that medical specialists use our diagnostic algorithm when evaluating individuals with peripheral neuropathic pain.

Early diagnosis of peripheral nervous system involvement in Fabry disease and treatment of neuropathic pain: the report of an expert panel

Background

Fabry disease is an inherited metabolic disorder characterized by progressive lysosomal accumulation of lipids in a variety of cell types, including neural cells. Small, unmyelinated nerve fibers are particularly affected and small fiber peripheral neuropathy often clinically manifests at young age. Peripheral pain can be chronic and/or occur as provoked attacks of excruciating pain. Manifestations of dysfunction of small autonomic fibers may include, among others, impaired sweating, gastrointestinal dysmotility, and abnormal pain perception. Patients with Fabry disease often remain undiagnosed until severe complications involving the kidney, heart, peripheral nerves and/or brain have arisen.

Methods

An international expert panel convened with the goal to provide guidance to clinicians who may encounter unrecognized patients with Fabry disease on how to diagnose these patients early using simple diagnostic tests. A further aim was to offer recommendations to control neuropathic pain.

Results

We describe the neuropathy in Fabry disease, focusing on peripheral small fiber dysfunction - the hallmark of early neurologic involvement in this disorder. The clinical course of peripheral pain is summarized, and the importance of medical history-taking, including family history, is highlighted. A thorough physical examination (e.g., angiokeratoma, corneal opacities) and simple non-invasive sensory perception tests could provide clues to the diagnosis of Fabry disease. Reported early clinical benefits of enzyme replacement therapy include reduction of neuropathic pain, and adequate management of residual pain to a tolerable and functional level can substantially improve the quality of life for patients.

Conclusions

Our recommendations can assist in diagnosing Fabry small fiber neuropathy early, and offer clinicians guidance in controlling peripheral pain. This is particularly important since management of pain in young patients with Fabry disease appears to be inadequate.

Social-adaptive and psychological functioning of patients affected by Fabry disease

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by the deficiency of alpha-galactosidase A. In addition to the debilitating physical symptoms of FD, there are also under-recognized and poorly characterized psychiatric features. As a first step toward characterizing psychiatric features of FD, we administered the Achenbach adult self report questionnaire to 30 FD patients and the Achenbach adult behavior checklist questionnaire to 28 partners/parents/friends of FD patients. Data from at least one of the questionnaires were available on 33 subjects. Analysis focused on social-adaptive functioning in various aspects of daily life and on criteria related to the Diagnostic and statistical manual of mental disorders IV (DSM-IV). Adaptive functioning scale values, which primarily measure social and relationship functioning and occupational success, showed that eight FD patients (six female and two male) had mean adaptive functioning deficits as compared to population norms. Greater rates of depression (P < 0.01), anxiety (P = 0.05), depression and anxiety (P = 0.03), antisocial personality (P < 0.001), attention-deficit/hyperactivity (AD/H; P < 0.01), hyperactivity-impulsivity (P < 0.01), and aggressive behavior (P = 0.03) were associated with poorer adaptive functioning. Decreased social-adaptive functioning in this study was not statistically significantly associated to disease severity, pain, or level of vitality. This study shows for the first time that FD patients, particularly women, are affected by decreased social-adaptive functioning. Comprehensive treatment plans for FD should consider assessments and interventions to evaluate and improve social, occupational, and psychological functioning. Attention to the behavioral aspects of FD could lead to improved treatment outcome and improved quality of life. Individuals affected by Fabry disease exhibited social-adaptive functioning deficits that were significantly correlated with anxiety, depression, antisocial behavior, and AD/H problems in a sampling of our male and female patients aged between 18 years and 59 years.

Substrate reduction augments the efficacy of enzyme therapy in a mouse model of Fabry disease

Fabry disease is an X-linked glycosphingolipid storage disorder caused by a deficiency in the activity of the lysosomal hydrolase α-galactosidase A (α-gal). This deficiency results in accumulation of the glycosphingolipid globotriaosylceramide (GL-3) in lysosomes. Endothelial cell storage of GL-3 frequently leads to kidney dysfunction, cardiac and cerebrovascular disease. The current treatment for Fabry disease is through infusions of recombinant α-gal (enzyme-replacement therapy; ERT). Although ERT can markedly reduce the lysosomal burden of GL-3 in endothelial cells, variability is seen in the clearance from several other cell types. This suggests that alternative and adjuvant therapies may be desirable. Use of glucosylceramide synthase inhibitors to abate the biosynthesis of glycosphingolipids (substrate reduction therapy, SRT) has been shown to be effective at reducing substrate levels in the related glycosphingolipidosis, Gaucher disease. Here, we show that such an inhibitor (eliglustat tartrate, Genz-112638) was effective at lowering GL-3 accumulation in a mouse model of Fabry disease. Relative efficacy of SRT and ERT at reducing GL-3 levels in Fabry mouse tissues differed with SRT being more effective in the kidney, and ERT more efficacious in the heart and liver. Combination therapy with ERT and SRT provided the most complete clearance of GL-3 from all the tissues. Furthermore, treatment normalized urine volume and uromodulin levels and significantly delayed the loss of a nociceptive response. The differential efficacies of SRT and ERT in the different tissues indicate that the combination approach is both additive and complementary suggesting the possibility of an improved therapeutic paradigm in the management of Fabry disease.

Painful peripheral neuropathies

Peripheral neuropathies are a heterogeneous group of diseases affecting peripheral nerves. The causes are multiple: hereditary, metabolic, infectious, inflammatory, toxic, traumatic. The temporal profile includes acute, subacute and chronic conditions. The majority of peripheral neuropathies cause mainly muscle weakness and sensory loss, positive sensory symptoms and sometimes pain. When pain is present, however, it is usually extremely intense and among the most disabling symptoms for the patients. In addition, the neurological origin of the pain is often missed and patients receive inadequate or delayed specific treatment. Independently of the disease causing the peripheral nerve injury, pain originating from axonal pathology or ganglionopathy privileges neuropathies affecting smaller fibres, a clinical observation that points towards abnormal activity within nociceptive afferents as a main generator of pain. Natural activation of blood vessels or perineurial nociceptive network by pathology also causes intense pain. Pain of this kind, i.e. nerve trunk pain, is among the heralding symptoms of inflammatory or ischemic mononeuropathy and for its intensity represents itself a medical emergency. Neuropathic pain quality rekindles the psychophysical experience of peripheral nerves intraneural microstimulation i.e. a combination of large and small fibres sensation temporally distorted compared to physiological perception evoked by natural stimuli. Pins and needles, burning, cramping mixed with numbness, and tingling are the wording most used by patients. Nociceptive pain instead is most often described as aching, deep and dull. Good command of peripheral nerve anatomy and pathophysiology allows timely recognition of the different pain components and targeted treatment, selected according to intensity, type and temporal profile of the pain.

Corneal confocal microscopy: a novel noninvasive means to diagnose neuropathy in patients with Fabry disease

Neuropathy is a cause of significant disability in patients with Fabry disease, yet its diagnosis is difficult. In this study we compared the novel noninvasive techniques of corneal confocal microscopy (CCM) to quantify small-fiber pathology, and non-contact corneal aesthesiometry (NCCA) to quantify loss of corneal sensation, with established tests of neuropathy in patients with Fabry disease. Ten heterozygous females with Fabry disease not on enzyme replacement therapy (ERT), 6 heterozygous females, 6 hemizygous males on ERT, and 14 age-matched, healthy volunteers underwent detailed quantification of neuropathic symptoms, neurological deficits, neurophysiology, quantitative sensory testing (QST), NCCA, and CCM. All patients with Fabry disease had significant neuropathic symptoms and an elevated Mainz score. Peroneal nerve amplitude was reduced in all patients and vibration perception threshold was elevated in both male and female patients on ERT. Cold sensation (CS) threshold was significantly reduced in both male and female patients on ERT (P < 0.02), but warm sensation (WS) and heat-induced pain (HIP) were only significantly increased in males on ERT (P < 0.01). However, corneal sensation assessed with NCCA was significantly reduced in female (P < 0.02) and male (P < 0.04) patients on ERT compared with control subjects. According to CCM, corneal nerve fiber and branch density was significantly reduced in female (P < 0.03) and male (P < 0.02) patients on ERT compared with control subjects. Furthermore, the severity of neuropathic symptoms and the neurological component of the Mainz Severity Score Index correlated significantly with QST and CCM. This study shows that CCM and NCCA provide a novel means to detect early nerve fiber damage and dysfunction, respectively, in patients with Fabry disease.

Fabry's disease

Fabry's disease is an X-linked lysosomal storage disorder caused by abnormalities in the GLA gene, which leads to a deficiency in alpha-galactosidase A. The consequent abnormal accumulation of glycosphingolipids results in several clinical signs and symptoms and substantial morbidity and mortality. This review covers all basic aspects of the disease such as epidemiology, pathophysiology, clinical presentation by systems, diagnosis, management, prevention, and repercussions on quality of life. With the development of enzyme replacement therapy in the past few years, early initiation of treatment is key for improvement in major affected organs with decreased cardiac mass and stabilisation of kidney function, and improvement in neuropathic pain, sweating, gastrointestinal symptoms, hearing loss, and pulmonary symptoms. However, treatment of individual symptoms in addition to enzyme replacement therapy seems to be needed for many patients, especially those who have had some degree of organ dysfunction. Additional data are needed to document long-term treatment outcomes.

Osteopenia: a common aspect of Fabry disease. Predictors of bone mineral density

PURPOSE

We investigated the bone mineral status in patients with untreated Fabry disease (FD).

METHODS

Descriptive, cross-sectional study in 53 patients with FD investigating bone mineral density (BMD)/content (dual energy x-ray absorptiometry scan), bone metabolism (parathyroid hormone, osteocalcin, and insulin-like growth factor I), and renal function (ethylene diamine tetraacetic acid clearance).

RESULTS

Mean BMD z score at the lumbar spine and femoral neck were -0.05 +/- 1.46 SD and -0.37 +/- 1.02 SD, respectively. Approximately 50% had osteopenia in the hip or lumbar spine and additionally four had osteoporosis. Multivariate analysis including body weight, impaired renal function, and genotype overall explained 48% of the variance in lumbar spine BMD (P < 0.001), whereas body weight, impaired renal function, and menopausal status in the female population accounted for more than 50% of the variation in BMD of both the lumbar spine and femoral neck (both P < 0.001). Twenty percent of patients had hyperparathyroidism. Although the level of parathyroid hormone was significantly associated with impaired renal function, osteocalcin levels were significantly higher in patients with lumbar spine osteopenia or osteoporosis than in those with normal BMD.

CONCLUSIONS

Osteopenia was present in approximately 50% of patients with untreated FD. Whether BMD and bone metabolism will improve after enzyme replacement therapy remains to be established.

Misleading terms in Anderson-Fabry disease

BACKGROUND

Signs and symptoms of classic Fabry disease manifest itself on the skin (angiokeratoma), the nervous system (acroparaesthesia), the heart (restrictive cardiomyopathy) and a variety of other organs.

MATERIALS AND METHODS

Diagnosis of Fabry disease was confirmed by genetic tests in a cohort of 100 patients and a standardized examination programme was performed in all patients. We were puzzled when applying well-established and textbook-anchored signs and symptoms to our patients.

RESULTS

Among the 47 male and 53 female patients (mean age 41 +/- 16 years) with genetically proven disease, the Fabry-type vascular skin lesions were without hyperkeratotic aspect and keratomas were virtually absent. The peripheral neuropathic pain found in all male patients was not compatible with the wording 'acro' and 'paraesthesia', suggesting a different pathophysiological mechanism. Upon echocardiographic examination, patients mainly revealed diastolic relaxation abnormalities of the heart and only one patient had a restrictive cardiac pattern.

CONCLUSIONS

Our findings suggest that some terms used to describe signs and symptoms of Fabry disease are historically derived and do not comply with state-of-the-art examination. We propose to replace the term 'angiokeratoma' with 'angioma', the term 'acroparaesthesia' with 'neuropathic pain' and the term 'restrictive cardiomyopathy' with 'cardiac hypertrophic storage disease'. As most of the physicians are not familiar with Fabry disease, terms used in the past might prevent the correct diagnosis of a potentially treatable disease.

Females with Fabry disease frequently have major organ involvement: lessons from the Fabry Registry

Fabry disease (FD) is an X-linked lysosomal storage disease caused by alpha-galactosidase A deficiency. The Fabry Registry is a global clinical effort to collect longitudinal data on FD. In the past, most "carrier" females were usually thought to be clinically unaffected. A systematic effort has been made to enroll all FD females, regardless of symptomology. Of the 1077 enrolled females in the Registry, 69.4% had symptoms and signs of FD. The median age at symptom onset among females was 13 years, and even though 84.1% had a positive family history, the diagnosis was not made until a median age of 31 years. Twenty percent experienced major cerebrovascular, cardiac, or renal events, at a median age of 46 years. Among adult females with estimated glomerular filtration rate (eGFR) data (N=638), 62.5% had an eGFR <90 ml/min/1.73 m2 and 19.0% had eGFR <60 ml/min/1.73 m2. Proteinuria 300 mg/day was present in 39.0% of females, and 22.2% had >1 gram/day. Quality of life (QoL), as measured by the SF-36((R)) survey, was impaired at a later age than in males, but both genders experience significantly impaired QoL from the third decade of life onward. Thus, females with FD have a significant risk for major organ involvement and decreased QoL. Females should be regularly monitored for signs and symptoms of FD, and considered for enzyme replacement therapy.

Heterozygous Fabry women are not just carriers, but have a significant burden of disease and impaired quality of life

PURPOSE

To determine if there is significant symptomatology in women with heterozygous alpha-galactosidase mutations.

METHODS

Data from medical records of the 44 heterozygous females followed at Cedars-Sinai Medical Center were compiled and analyzed for symptoms of Fabry disease. Quality of life data were also analyzed.

RESULTS

Seventy-six percent were referred due to an affected male relative; 76% reported acroparesthesias as their first symptom. A mean of 15.7 years elapsed from onset of first symptoms to the diagnosis. Quality of life, measured by the SF-36 survey, was globally reduced. Pain affected mood and enjoyment of life. Central/peripheral nervous, cardiopulmonary, and renal system manifestations of Fabry disease were present far above that predicted for random X-inactivation of the normal allele. Fatigue, present in 59%, was associated with reduced maximum oxygen consumption (P=0.049); exercise intolerance, present in 83%, was associated with reduced maximal heart rate during exercise testing (P=0.0089). Women diagnosed via family history experienced more angina (P=0.035), decreased vibration sense (P=0.026), and had a worse percentage predicted FEF25-75 (P=0.037) compared to women diagnosed because of symptoms.

CONCLUSIONS

This study indicates that the asymptomatic female carrier of Fabry disease is the exception, not the rule: heterozygotes suffer from significant multisystemic disease and reduced quality of life and must be monitored and treated accordingly.

A survey of the pain experienced by males and females with Fabry disease

BACKGROUND

The clinical onset of Fabry disease, a rare, X-linked, multisystemic disorder, is marked by neuropathic pain. Males suffer extensively from this disease. Females, as genetic 'carriers', have traditionally been viewed as either asymptomatic or mildly afflicted with this disease.

OBJECTIVES

To describe Fabry-related pain and compare experiences between the sexes. Patients' perceptions of physician pain assessments were also examined.

METHODS

A disease-specific questionnaire was accessible on-line (www.fabry.org) and mailed to 552 members of a Fabry disease support group.

RESULTS

The response rate was 14.3% for the support group-based mail questionnaire. Females (58.0%) were significantly older (mean +/- SD 45.9+/-13.5 years) than males (mean +/- SD 40.0+/-12.1; t [86]=-2.11, P<0.05). Females were diagnosed with Fabry disease later (31.1+/-14.0 years) than males (24.2+/-11.9 years; t [86]=-2.43, P<0.05). Females (mean score for pain disability rating 3.0+/-1.4) suffered more extensive disability from migraine pain (mean score 2.2+/-1.3; F [1, 74]=45.0, P<0.005), and, unlike males, did not exhibit a decline in pain intensity with disease duration. Satisfaction with physician pain assessments was moderate.

CONCLUSIONS

Contrary to the traditional view of females as carriers, females with Fabry disease experienced intense disease-related pain; pain produced comparable distress and impairment in both sexes. The diagnostic delay and absence of a decline in pain symptoms over time in females suggest additional disease burden. Females may be triply disadvantaged in the health care system due to disease rarity, devalued carrier status and sex.

Improvement of sympathetic skin responses under enzyme replacement therapy in Fabry disease

AIM

To report the effect of enzyme replacement therapy (ERT) in sympathetic skin responses (SSR) of patients with Fabry disease.

PATIENTS AND METHODS

Seven male patients were included in an open-label protocol using agalsidase-alfa, continued at regular intervals. Five patients completed 24 months of ERT and two of them completed 18 months. Two main measurements were performed at baseline, as well as 1 and 2 years after ERT: (1) a standard neurological examination (NE), with a detailed evaluation of the sensory perception of light touch, pinprick, cold, hot, and vibratory stimuli; (2) the SSR amplitudes.

RESULTS

Although there were no significant differences between NE in this time period, all patients reported general improvement in their subjective reports of acroparaesthesia and sweating. Before starting ERT, the SSR amplitudes were either too small (3/7 patients) or absent (4/7 patients): the average (range) amplitude of 122 microV (0 through 492) was statistically smaller than that found in a control group, i.e. 1453.6 microV (619.7-2754) (p<0.0001, t-test). Mean +/- SD SSR amplitude increased to 1088+/- 690 microV in the second year of ERT, reaching the range found in a normal control group (p=0.004).

CONCLUSION

ERT improved SSR continuously in Fabry patients in 2 years of observation. Although the mechanism of the SSR improvement is unknown, this response to ERT can be clinically significant if it reflects a normalization in sweating.

[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.

Enzyme-replacement therapy with agalsidase alfa in children with Fabry disease

CONTEXT

Fabry disease is an X-linked multisystem disorder. Enzyme-replacement therapy in adults has limited efficacy in treating major sequelae of advanced Fabry disease, such as kidney failure or stroke. This prompted a study of the safety and efficacy of enzyme replacement at an earlier stage of Fabry disease.

OBJECTIVES

Our purpose with this work was to evaluate safety and to explore efficacy of enzyme treatment with agalsidase alfa in pediatric patients with Fabry disease.

METHODS

We conducted a 6-month open-label study at 3 tertiary care centers with 24 children (19 boys and 5 girls) with a mean age of 11.8 (range: 6.5-18) years, to examine safety parameters, including infusion reactions and antiagalsidase alfa antibodies.

RESULTS

Agalsidase alfa was well tolerated, and all of the patients completed the study. Six boys and 1 girl had mild-to-moderate infusion reactions. One boy developed transient immunoglobulin G antibodies against agalsidase alfa. The boys showed a significant reduction in plasma globotriaosylceramide on treatment. Mean estimated glomerular filtration rate, cardiac structure, and function were normal and did not change over 26 weeks. Heart rate variability, as determined by 2-hour ambulatory monitoring, was decreased in the boys compared with the girls at baseline. All indices of heart rate variability improved significantly in the boys. Three patients with anhidrosis, as determined by quantitative sudomotor axon reflex testing, developed sweating. Six of 11 patients could reduce or cease their use of antineuropathic analgesics.

CONCLUSIONS

Enzyme replacement with agalsidase alfa was safe in this study. The exploratory efficacy analysis documented increased clearance of globotriaosylceramide and improvement of autonomic function. Prospective long-term studies are needed to assess whether enzyme replacement initiated early in patients with Fabry disease is able to prevent major organ failure in adulthood.

Neuropathy and Fabry's disease

Fabry's disease is a multisystem disorder that is commonly associated with a painful, debilitating neuropathy. The common coexistence of arthralgias and an elevated erythrocyte sedimentation rate may lead to the misdiagnosis of a rheumatic condition. We report a 38-year-old man who was evaluated for progressive neuropathy and limb pain in the setting of longstanding arthralgias, presumed juvenile rheumatoid arthritis, and past renal transplantation. Histopathologic assessment of nerve and muscle biopsy specimens led to the diagnosis of Fabry's disease, thus allowing the patient to receive enzyme replacement therapy that may slow progression and preserve the transplanted kidney.

Monitoring the clinical and biochemical response to enzyme replacement therapy in three children with Fabry disease

Fabry disease is an X-linked disorder of glycosphingolipid metabolism resulting from a deficiency of the lysosomal enzyme alpha-galactosidase A. This leads to the progressive accumulation of glycosphingolipids in lysosomes of most visceral tissues and in body fluids. Following successful clinical trials in adults, two recombinant enzyme preparations of alpha-galactosidase have recently been licensed in Europe for the treatment of Fabry disease and treatment in children has commenced. We now report the clinical findings and the levels of globotriaosylceramide in plasma and urine in three boys who have been treated with enzyme replacement therapy (agalsidase beta, Fabrazyme), 1 mg/kg for 2 years. In one boy there was a rapid improvement in all the clinical and biochemical parameters measured. This has been maintained. In the other two boys, who are siblings, there was no measurable clinical improvement after 1 year and the levels of globotriaosylceramide in plasma and urine, although lower than before treatment, were still considerably elevated. There was no evidence of blocking or neutralising antibodies so the dose of enzyme was increased to 2 mg/kg at 74 weeks of therapy. At 2 years their pain scores had improved but this was not accompanied by any reduction in the plasma or urine globotriaosylceramide levels.

CONCLUSION

Measurement of globotriaosylceramide in plasma and urine may not be the most appropriate marker to monitor the progression of treatment by enzyme replacement therapy in all patients. Certainly the subjective clinical improvement in the two brothers in this report outweighed the objective biochemical findings.

Head-impulse testing in Fabry disease--vestibular function in male and female patients

AIM

To study the prevalence of peripheral vestibular deficit in male and female patients with Fabry disease and to assess the effect of enzyme replacement therapy (ERT) on peripheral vestibular function using quantitative head-impulse testing.

METHODS

Using dual search-coils the vestibulo-ocular reflex during rapid rotational head thrusts to both sides was recorded in 21 patients (13 male, 8 female) with Fabry disease prior to ERT initiation. ERT consisted of infusions of gene-activated human alpha-galactosidase A (agalsidase alfa; Replagal) every 2 weeks at doses of 0.2 mg/kg. Eight patients were tested again approximately 6 and 12 months after the initiation of ERT.

RESULTS

At baseline examination, 15 of the patients with Fabry disease (71%; 11 males, 4 females) showed reduced peripheral vestibular function. The deficit was unilateral in nine patients (3 females) and bilateral in six patients (1 female). The severity of the vestibular deficit was not significantly different between male and female patients. After 12 months of ERT, the average vestibular deficit on the weaker side tended to improve; however, the change was not significant (p = 0.10).

CONCLUSION

Fabry disease affects peripheral vestibular function in both male and female patients. Females seem to be affected less frequently than males, but, on average, vestibular deficits are not different between the two groups. To confirm or reject the tendency for vestibular improvement during ERT, more patients need to be tested and longer follow-up periods are required.

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.