Assessment of renal pathology and dysfunction in children with Fabry disease

Fabry App: the value of a portable technology in recording day-to-day patient monitored information in patients with Fabry disease

BACKGROUND

Fabry disease is a rare inherited disorder resulting from deficient α-galactosidase A enzyme activity. Common disease manifestations are sweating abnormalities, neuropathic pain, gastrointestinal symptoms and fatigue. Challenges are faced by health care professionals in evaluating symptom burden in the current clinical setting, and the demand for alternative methods for monitoring disease-specific symptoms has seen an acceleration in recent years. Smartphone technologies offer the potential for continuity of care and surveillance. As a part of a quality improvement project, a disease specific app was developed in collaboration with a software company (Health Touch Ltd) and made available for patient use in May 2018. The Fabry mobile app records five categories: pain, gastrointestinal symptoms, sweating, activity levels, medications. Fabry disease patients with gastrointestinal and pain symptoms attending the Lysosomal Storage Disorders Unit of the Royal Free London NHS Foundation Trust were reviewed to assess eligibility and invited to download the app for recording their symptoms (activity, sweating, pain and gastrointestinal) and medications. Patient-generated data were transmitted to a secure website for clinicians to review.

RESULTS

One-hundred and thirty-nine symptomatic Fabry disease patients who had a smartphone (iPhone or android) were invited to download the app. Sixty-seven patients (26 males and 41 females; median age, 49 years [range, 20-81]) downloaded and tracked the Fabry App at least once. The median frequency of use per patient was 6 (range, 1-629). Pain in the hands and abdominal pain were significantly higher (p = 0.009 and p = 0.007, respectively) in patients with classic phenotype compared with patients with non-classic phenotypes.

CONCLUSIONS

We demonstrated the feasibility and acceptability of a smartphone app to facilitate the remote assessment and monitoring of Fabry disease symptom burden on a daily/weekly basis, as an alternative to the current standard of care that requires patients to recall their symptoms during 6 to 12 monthly annual clinic visits. Patients who were more likely to use the app had greater disease burden. This innovation has the potential to assess disease progression, early therapeutic intervention, thereby decreasing the burden of morbidity and mortality among Fabry patients, and to record long-term effects of Fabry-specific therapies.

Concurrent fabry disease and immunoglobulin a nephropathy: a case report

BACKGROUND

Fabry disease (FD) is an X-linked, hereditary dysfunction of glycosphingolipid storage caused by mutations in the GLA gene encoding alpha-galactosidase A enzyme. In rare cases, FD may coexist with immunoglobulin A nephropathy (IgAN). We describe a case of concurrent FD, IgAN, and dilated cardiomyopathy-causing mutations in the TTN and BAG3 genes, which has not been reported previously.

CASE PRESENTATION

A 60-year-old female patient was admitted with a one-week history of facial and lower-limb edema, two-year history of left ventricular hypertrophy and sinus bradycardia, and recurring numbness and pain in three lateral digits with bilateral thenar muscle atrophy. Renal biopsy revealed concurrent FD (confirmed via an alpha-galactosidase A enzyme assay, Lyso-GL-3 quantification, and GLA gene sequencing) and IgAN. Heterozygous mutations in the TTN (c.30,484 C > A;p.P10162T) and BAG3 (c.88 A > G;p.I30V) genes were observed. The patient reported that two of her brothers had undergone kidney transplantation; one died suddenly at 60 years of age, and the other required a cardiac pacemaker. The 35-year-old son of the patient was screened for the GLA gene mutation and found to be positive for the same mutation as the patient. The patient was administered oral losartan (50 mg/day). Enzyme replacement therapy was refused due to financial reasons. Her renal and cardiac functions were stable yet worth closely monitoring during follow-up.

CONCLUSION

The family history of patients with concurrent heart and renal diseases should be assessed in detail. Genetic testing and histological examinations are essential for diagnosing FD with IgAN.

The evolution of the initial manifestations and renal involvement of chinese patients with classical and late-onset Fabry disease at different sexes and ages

BACKGROUND

Fabry disease is a rare hereditary disease involving multiple organs, and there are few reports on how the initial manifestations and renal involvement of these patients with classical and late-onset phenotype evolve with sexes and ages. To improve clinicians' understanding of Fabry disease and avoid misdiagnoses by discussing the initial manifestations, first medical specialties visited and renal involvement development in patients.

METHODS

This study collected relevant data from 311 Chinese Fabry disease patients (200 males, 111 females) and descriptive statistical analysis was used to analyze the evolution of the initial manifestations and renal involvement of patients with classical and late-onset phenotype at different sexes and ages.

RESULTS

Regarding the age at manifestation onset, age at the first medical specialty visited and age at the diagnosis of Fabry disease, males were earlier than females, and males with classical phenotype were earlier than males with late-onset and females with classical phenotype. In both male and female patients, the initial manifestations of classical patients were mainly acroparesthesia, and the first medical specialty visited were mainly pediatrics and neurology. The initial manifestations of late-onset patients were mainly renal and cardiovascular involvement, and the first medical specialty visited were mainly nephrology and cardiology. In classical patients, both male and female, the initial manifestations of the preschool and the juvenile groups were mainly acroparesthesia, and the frequency of renal and cardiovascular involvement in the young group was higher than that in the preschool and juvenile groups. There was no obvious renal involvement in the preschool group, renal involvement was most common in the young group and the middle-aged and elderly group. Proteinuria can appear in classical male patients as early as approximately 20 years, and renal insufficiency can occur at approximately 25 years. With age, over 50% of classical male patients can develop varying degrees of proteinuria at the age of 25 and renal insufficiency at the age of 40. 15.94% of the patients progressed to dialysis or kidney transplantation, mainly classical males.

CONCLUSIONS

The initial manifestation of Fabry disease is affected by sex, age and classical/late-onset phenotype. The initial manifestations were mainly acroparesthesia and the frequency and degree of renal involvement increased gradually with aging in classical male patients.

Clinical outcomes among young patients with Fabry disease who initiated agalsidase beta treatment before 30 years of age: An analysis from the Fabry Registry

BACKGROUND

Clinical manifestations of classic Fabry disease (α-galactosidase A deficiency) usually occur in childhood, while complications involving major organs typically develop in adulthood. Outcomes of Fabry-specific treatment among young patients have not been extensively reported. Our aim was to analyze clinical outcomes among patients aged 5-30 years at initiation of treatment with agalsidase beta using data from the Fabry Registry (NCT00196742, sponsor: Sanofi).

METHODS

Reported GLA variants were predicted to be associated with the classic phenotype or not classified in fabry-database.org. Linear mixed models were conducted to assess changes over ≥2-year follow-up in the estimated glomerular filtration rate (eGFR) stratified by low (LRI) and high (HRI) renal involvement (defined by proteinuria/albuminuria levels), and changes in interventricular septal thickness (IVST) and left ventricular posterior wall thickness (LVPWT) Z-scores stratified by median age at first treatment. Self-reports ('yes'/'no') of abdominal pain, diarrhea, chronic peripheral pain (denoting neuropathic pain), and acute pain crises at baseline were compared with reports after ≥0.5-year and ≥2.5-year follow-up using McNemar's test.

RESULTS

Male (n = 117) and female patients (n = 59) with LRI initiated treatment at a median age of 19.9 and 23.6 years, respectively, and were followed for a median of 6.3 and 5.0 years, respectively. The eGFR slopes were -1.18 (P_{from 0} <0.001) and -0.92 mL/min/1.73 m²/year (P_{from 0} = 0.040), respectively. Males with HRI (n = 23, median UPCR 1.0 g/g), who started treatment at a median age of 26.7 years, had an eGFR slope of -2.39 mL/min/1.73 m²/year (P_{from 0} <0.001; P_difference = 0.055, as compared with the slope of -1.18 mL/min/1.73 m²/year for LRI males) during a median follow-up of 5.6 years. Echocardiographic variables were stable among males, regardless of age, and among young females (median follow-up >5.5 years and ≥4.5 years, respectively). Older females (treatment initiation at median age 27.5 years) had a slope of LVPWT Z-scores of 0.18/year (n = 12, P_{from 0} = 0.028), whereas IVST Z-scores remained stable (n = 13, 0.10/year, P_{from 0} = 0.304) during a median follow-up of ≥3.7 years. These slopes did not significantly differ from slopes of younger females. Reports of chronic peripheral pain and acute pain crises by males, and of diarrhea and acute pain crises by females, significantly reduced after a median follow-up of ≥4.0 years. After a median follow-up of ≥5.4 years, reports of all four symptoms significantly decreased among males, whereas among females only reports of abdominal pain significantly decreased.

CONCLUSIONS

During sustained treatment with agalsidase beta in young Fabry patients with a predicted classic phenotype or with unclassified GLA variants with similar characteristics, the decline in eGFR was modest among male and female patients with LRI. The greater decline in eGFR among older, proteinuric (i.e., HRI) males may suggest a benefit of earlier treatment. Overall, echocardiographic variables remained stable, particularly among males and younger females. Significant reductions in symptom reports occurred primarily among males after longer follow-up and were less noticeable among females. These observed trends are suggestive of an overall improvement after treatment in young patients, but warrant larger longitudinal studies.

Clinical features and enzyme replacement therapy in 10 children with Fabry disease

OBJECTIVE

To summarize the clinical features, diagnosis and enzyme replacement therapy(ERT) of Fabry disease (FD) in children.

METHODS

The clinical data, laboratory tests, genetic variations and treatment of 10 FD children diagnosed in Shandong Provincial Hospital from September 2020 to June 2022 were retrospectively analyzed.

RESULTS

Among the 10 cases from 6 families, 7 patients were boys of 4 to 13 years of age, and 3 were girls of 12 to 15 years of age. There were 7 symptomatic patients, including 6 boys and 1 girl. All 7 patients presented with acral neuralgia. Five patients had little or no sweating. Five patients presented with cutaneous angiokeratoma. Two patients had abdominal pain. One patient developed joint symptoms. Four patients had corneal opacity. One patient had hearing loss; one patient had short stature. One patient had mild proteinuria and 1 patient had dysplasia of the right kidney with decreased eGFR (55.28 ml/min.1.73 m²). The left ventricular mass index was slightly elevated in 1 patient. Three patients had mild obstructive ventilatory dysfunction; a small amount of effusion in the intestinal space of the lower abdomen or mild fatty liver was found in 2 patients. Partial empty sella turcica in 1 patient. A total of 6 GLA gene variants were detected in 10 children, among which C.1059_1061delGAT (p.met353del) was a newly discovered mutation. Five children received ERT, of which 4 were treated with agalsidase beta and 1 was treated with agalsidase alpha. Only 1 patient had anaphylaxis. Lyso-GL-3 levels decreased significantly in the first 3 months of ERT initiation and remained relatively stable thereafter in 3 patients. The Lyso-GL-3 level was decreased, but renal impairment continued to progress in 1 patient treated with agalsidase alpha.

CONCLUSION

The clinical manifestations of FD in childhood are diverse, and it is necessary to make a definite diagnosis by combining family history, enzyme activity, biomarkers, gene testing and other indicators. Pedigree screening and high-risk population screening are helpful for early identification, early diagnosis and early treatment. No serious adverse reactions were found during the short-term treatment with agalsidase alpha and beta.

Expert opinion on the recognition, diagnosis and management of children and adults with Fabry disease: a multidisciplinary Turkey perspective

This consensus statement by a panel of Fabry experts aimed to identify areas of consensus on conceptual, clinical and therapeutic aspects of Fabry disease (FD) and to provide guidance to healthcare providers on best practice in the management of pediatric and adult patients with FD. This consensus statement indicated the clinical heterogeneity of FD as well as a large number of pathogenic variants in the GLA gene, emphasizing a need for an individualized approach to patient care. The experts reached consensus on the critical role of a high index of suspicion in symptomatic patients and screening of certain at-risk groups to reveal timely and accurate diagnosis of FD along with an increased awareness of the treating physician about the different kinds of pathogenic variants and their clinical implications. The experts emphasized the crucial role of timely recognition of FD with minimal delay from symptom onset to definite diagnosis in better management of FD patients, given the likelihood of changing the disease's natural history, improving the patients' quality of life and the prognosis after enzyme replacement therapy (ERT) administered through a coordinated, multidisciplinary care approach. In this regard, this consensus document is expected to increase awareness among physicians about unique characteristics of FD to assist clinicians in recognizing FD with a well-established clinical suspicion consistent with pathogenic variants and gender-based heterogeneous clinical manifestations of FD and in translating this information into their clinical practice for best practice in the management of patients with FD.

Recommendations for the diagnosis and management of Fabry disease in pediatric patients: a document from the Rare Diseases Committee of the Brazilian Society of Nephrology (Comdora-SBN)

Abstract Fabry disease (FD) is a genetic disease, with X-chromosome linked inheritance, due to variants in the GLA gene that encodes the α-galactosidase A (α-GAL) enzyme. The purpose of the present study was to create a consensus aiming to standardize the recommendations regarding the renal involvement of FD with guidelines on the diagnosis, screening, and treatment of pediatric patients. This consensus is an initiative of the Rare Diseases Committee (Comdora) of the Brazilian Society of Nephrology (SBN). Randomized controlled clinical studies and studies with real-life data added to the authors' experience were considered for this review. The result of this consensus was to help manage patient and physician expectations regarding treatment outcomes. Thus, this consensus document recommends the investigation of the pediatric family members of an index case, as well as cases with suggestive clinical signs. From the diagnosis, assess all possible FD impairments and grade through scales. From an extensive review of the literature including pediatric protocols and particularly evaluating pediatric cases from general studies, it can be concluded that the benefits of early treatment are great, especially in terms of neuropathic pain and renal impairment parameters and outweigh the possible adverse effects that were mainly manifested by infusion reactions.

Fabry disease and kidney involvement: starting from childhood to understand the future

The accumulation of globotriaosylceramide (Gb-3) in multiple organs, such as the heart, kidney, and nervous system, due to mutations in the galactosidase alpha (GLA) gene, represents the key point of Fabry disease (FD). The common symptoms appear in childhood or adolescence, including neuropathic pain, angiokeratoma, acroparesthesia, and corneal opacities. A multi-organ involvement induces a significant deterioration in the quality of life with high mortality in adulthood. The accumulation of Gb-3 involves all types of kidney cells beginning at fetal development, many years before clinical manifestations. A decline in the glomerular filtration rate is rare in children, but it can occur during adolescence. Pediatric patients rarely undergo kidney biopsy that could assess the efficacy of enzyme replacement therapy (ERT) behind its diagnostic role. To date, diagnosis is achieved by detecting reduced α-Gal-A activity in leukocytes and plasma, allowing for the early start of ERT. This review focuses on pediatric kidney involvement in FD, analyzing in depth its diagnostic processes and treatment options.

Clinical Characteristics, Renal Involvement, and Therapeutic Options of Pediatric Patients With Fabry Disease

Inherited renal diseases represent 20% of the causes of end-stage renal diseases. Fabry disease, an X-linked lysosomal storage disorder, results from α-galactosidase A deficient or absent activity followed by globotriaosylceramide (Gb3) accumulation and multiorgan involvement. In Fabry disease, kidney involvement starts early, during intrauterine life by the Gb3 deposition. Even if chronic kidney disease (CKD) is discovered later in adult life in Fabry disease patients, a decline in glomerular filtration rate (GFR) can occur during adolescence. The first clinical sign of kidney involvement is represented by albuminuria. So, early and close monitoring of kidneys function is required: albuminuria and proteinuria, urinary albumin-to-creatinine ratio, serum creatinine, or cystatin C to estimate GFR, while urinary sediment with phase-contrast microscopy under polarized light may be useful in those cases where leucocyte α-Gal A activity and GLA genotyping are not available. Children with Fabry disease and kidney involvement should receive enzyme replacement therapy and nephroprotective drugs (angiotensin-converting enzyme inhibitors or angiotensin receptor blockers) to prevent or slow the progressive loss of kidney functions. Early diagnosis of Fabry disease is important as enzyme replacement therapy reduces symptoms, improves clinical features and biochemical markers, and the quality of life. More importantly, early treatment could slow or stop progressive organ damage in later life.

Interstitial lung disease in lysosomal storage disorders

Lysosomes are intracellular organelles that are responsible for degrading and recycling macromolecules. Lysosomal storage diseases (LSDs) are a group of inherited diseases caused by mutations affecting genes that encode the function of the lysosomal enzymes. Three LSDs are associated with lung involvement and/or interstitial lung disease (ILD): Gaucher disease (GD); Niemann-Pick disease, also known as acid sphingomyelinase deficiency (ASMD); and Fabry disease (FD). In GD and in ASMD, analysis of bronchoalveolar lavage fluid and lung biopsy can be informative, showing foamy cells. In GD, ILD is rare. Enzyme replacement therapy (ERT) has been available since 1991 and has greatly changed the natural history of GD, with pulmonary failure and death reported before the ERT era. In ASMD, ILD is frequent and is usually associated with spleen enlargement, low platelet cell count and low level of high-density lipoprotein-cholesterol. Results of ERT are promising regarding preliminary results of olipudase alfa in paediatric and adult ASMD populations. The most frequent respiratory manifestation in FD is COPD-like symptoms regardless of smoking habit and dyspnoea due to congestive heart failure. Early diagnosis of these three LSDs is crucial to prevent irreversible organ damage. Early initiation of ERT can, at least in part, prevent organ failure.

Fabry disease-what cardiologists can learn from the nephrologist: a narrative review

Fabry disease (FD) is a rare, X-linked lysosomal storage disorder resulting in decreased or absent activity of the lysosomal enzyme alpha-galactosidase A. Subsequent accumulation of storage material can occur in virtually all cells of the body. Organs and structures affected by storage material deposition include the heart, the kidney, the central and peripheral nervous system and the cornea of the eyes. Progressive cardiac hypertrophy, arrhythmias, cardiac fibrosis, heart failure and cardiac death are common characteristics of cardiac involvement. Renal depositions of glycosphingolipids are already detectable in childhood. An early clinical sign of Fabry renal involvement is albuminuria, often preceding a detectable loss of kidney function. Later in life Fabry patients may exhibit a progressive decline of their kidney function leading to end-stage renal disease (ESRD). The clinical presentation of Fabry patients regarding renal involvement depends on the underlying mutation in the GLA gene. Classically affected males typically show a gradual decrease in kidney function, patients with mild or late onset mutations as well as a subgroup of females may exhibit only little or no renal abnormalities. This review summarizes the characteristics of renal involvement in FD, the diagnostics necessary to evaluate the degree of renal impairment and possible treatment options.

Biomarkers of Fabry Nephropathy: Review and Future Perspective

Progressive nephropathy is one of the main features of Fabry disease, which largely contributes to the overall morbidity and mortality burden of the disease. Due to the lack of specific biomarkers, the heterogeneity of the disease, and unspecific symptoms, diagnosis is often delayed. Clinical presentation in individual patients varies widely, even in patients from the same family carrying the same pathogenic GLA variant. Therefore, it is reasonable to anticipate that additional genomic, transcriptomic, proteomic, and metabolomics factors influence the manifestation and progression of the disease. The aim of this article is to provide an overview of nephropathy in Fabry patients and the biomarkers currently used in the diagnosis and follow-up. Current biomarkers are associated with late signs of kidney damage. Therefore, there is a need to identify biomarkers associated with early stages of kidney damage that would enable early diagnosis, which is crucial for effective treatment and prevention of severe irreversible complications. Recent advances in sequencing and -omics technologies have led to several studies investigating new biomarkers. We will provide an overview of the novel biomarkers, critically evaluate their clinical utility, and propose future perspectives, which we believe might be in their integration.

Clinical parameters, LysoGb3, podocyturia, and kidney biopsy in children with Fabry disease: is a correlation possible?

BACKGROUND

Fabry disease is an X-linked lysosomal storage disorder caused by α-galactosidase enzyme deficiency. We present clinical, biochemical, and histologic findings in children with classical phenotypic presentation of Fabry disease.

METHODS

A retrospective analysis was performed using charts from 14 children with confirmed diagnosis. Clinical parameters were evaluated. Globotriaosylsphingosine -lysoGb3- detection in plasma, podocyturia, and kidney biopsy were carried out in all cases.

RESULTS

All patients except one demonstrated at least one symptom of Fabry disease. LysoGb3 levels were above the normal range in all patients. Podocyturia was documented in all patients. Kidney biopsy revealed glomerular, interstitial, vascular, and tubular changes on light microscopy in nearly all patients. Electron microscopy showed podocyte inclusions in all patients.

CONCLUSIONS

No difference in symptomatology was discernible between boys and girls. Podocyturia was detectable in children serving as a possible early marker of kidney injury. LysoGb3 was elevated in all cases, emphasizing the importance for diagnosis especially in female patients with normal αGal A activity. A possible association between lysoGb3 and symptom severity and histological involvement in kidney biopsy should be assessed in prospective studies with enough statistical power to determine if lysoGb3 can be used to predict nephropathy in children with Fabry disease.

Investigation of correlation of urinary globotriaosylceramide (Gb3) levels with markers of renal function in patients with Fabry disease

Fabry disease (FD) is a disorder that results from mutations of hydrolase α-galactosidase A. The enzymatic defect leads to accumulation of globotriaosylceramide (Gb3) in the kidney. Substrate deposition is related to tissue damage in FD, but the relation of urinary Gb3 levels in patients and the renal function markers remain not completely understood. Once nephropathy is one of the main features of FD and is marked by an insidious development, we investigated a possible correlation of Gb3 with biochemical markers of nephropathy including albuminuria, estimated glomerular filtration rate (eGFR), serum creatinine and urea, and proteinuria in male and female patients under or not enzyme replacement therapy (ERT).Gb3, proteinuria and albuminuria were increased in male and female FD patients. We found no correlation between urinary Gb3 levels and all renal function parameters evaluated in Fabry patients (in both sexes and using or not ERT). On the other hand, albuminuria showed negative correlation with eGFR only in male under or not ERT, demonstrating that albuminuria seems to be an early marker of renal function alteration. In conclusion, the results suggest that urinary Gb3 level does not reflect the renal function and that albuminuria is an important biomarker in male FD patients.

The management and treatment of children with Fabry disease: A United States-based perspective

Fabry disease is an inherited X-linked disorder that presents during childhood in male and female patients. Young patients may initially experience pain, hypohidrosis, and gastrointestinal symptoms. Other manifestations of Fabry disease, such as renal and cardiac disease, manifest later in adolescence or adulthood. In the pediatric population, renal damage is typically subclinical and identifiable only through biopsy. Specialists from the United States with expertise in Fabry disease convened during 2013-2014 in order to develop these consensus guidelines about the management and treatment of children with Fabry disease. The presence of symptoms in boys and girls of any age is an indication to begin therapy. Early treatment before the onset of potentially irreversible vital organ pathology is ideal. Asymptomatic children with Fabry mutations should be followed closely for the development of renal, cardiac, neurological, or gastrointestinal signs, symptoms, or laboratory changes, which would warrant treatment initiation. A comprehensive care plan should be implemented by the treating physicians to guide the management of children with Fabry disease.

Broad spectrum of Fabry disease manifestation in an extended Spanish family with a new deletion in the GLA gene

Background

Fabry disease (FD) is an X-linked inherited disease based on the absence or reduction of lysosomal-galactosidase (Gla) activity. The enzymatic defect results in progressive impairment of cerebrovascular, renal and cardiac function. Normally, female heterozygote mutation carriers are less strongly affected than male hemizygotes aggravating disease diagnosis.

Method

Close examination of the patients by renal biopsy, echo- and electrocardiography and MRI. Blood work and subsequent DNA analysis were carried out utilizing approved protocols for PCR and Sequencing. MLPA analysis was done to unveil deletions within the GLA gene locus. Quantitative detection of Glycolipids in patient plasma and urine were carried out using HPLC/MS-MS and ESI-MS.

Results

In the presented case, a female index patient led to the examination of three generations of a Spanish family. She presented with severe oto-cochlear symptoms and covert renal and cardiac involvement. While conventional sequencing failed to detect a causative mutation, MLPA analysis revealed a deletion within the GLA gene locus, which we were able to map to a region spanning exon 2 and adjacent intronic parts. The analysis of different biomarkers revealed elevated lyso-Gb3 levels in all affected family members.

Conclusion

Our findings highlight the broad intrafamilial spectrum of symptoms of FD and emphasise the need to use MLPA screening in symptomatic females without conclusive sequencing result. Finally, plasma lyso-Gb3 proved to be a reliable biomarker for the diagnosis of FD.

The renal biopsy in the genomic era

Renal biopsy was introduced in the 1950s. By 1980 the pathologic diagnostic criteria for the majority of medical kidney diseases known today, including pediatric diseases, were established using light, electron microscopy and immunohistochemistry. However, it has become clear that there are limitations in the morphologic evaluation, mainly because a given pattern of injury can be caused by different aetiologies and, conversely, a single aetiology may present with more than one histological pattern. An explosion in kidney disease research in the last 20-30 years has brought new knowledge from bench to bedside rapidly and resulted in new molecular and genetic tools that enhance the diagnostic and prognostic power of the renal biopsy. Genomic technologies such as polymerase chain reaction (PCR), in situ hybridization and oligonucleotide microarrays, collectively known as genomics, detect single or multiple genes underscoring the pathologic changes and revealing specific causes of injury that may require different treatment. The aims of this review are to (1) summarize current recommendations for diagnostic renal biopsies encompassing light microscopy, immunofluorescence or immunohistochemistry and electron microscopy; (2) address the limitations of morphology; (3) show current contributions of genomic technologies adjunct to the renal biopsy, and provide examples of how these may transform pathologic interpretation into molecular disease phenotypes.

Agalsidase benefits renal histology in young patients with Fabry disease

The effect of early-onset enzyme replacement therapy on renal morphologic features in Fabry disease is largely unknown. Here, we evaluated the effect of 5 years of treatment with agalsidase alfa or agalsidase beta in 12 consecutive patients age 7-33 years (median age, 16.5 years). We performed renal biopsies at baseline and after 5 years of enzyme replacement therapy; 7 patients had additional biopsies after 1 and 3 years. After a median of 65 months, biopsy findings from all patients showed total clearance of glomerular endothelial and mesangial cell inclusions, and findings from 2 patients showed complete clearance of inclusions from epithelial cells of the distal tubule. The 4 patients who received the highest dose of agalsidase exhibited substantial clearance of podocyte inclusions, and the youngest patient had nearly complete clearance of these inclusions. Linear regression analysis showed a highly significant correlation between podocyte globotriaocylceramide clearance and cumulative agalsidase dose (r=0.804; P=0.002). Microalbuminuria normalized in five patients. In summary, long-term enzyme replacement therapy in young patients can result in complete globotriaocylceramide clearance of mesangial and glomerular endothelial cells across all dosage regimens, and clearance of podocyte inclusions is dose-dependent.

X-inactivation in Fabry disease

BACKGROUND

Fabry disease is one of three X-linked lysosomal disorders. Because of X-chromosome inactivation (XCI), wherein there is (random) transcriptional silencing of one of the X-chromosomes in each female cell, females are mosaic for the expression of (some) X-linked genes. Thus, based on penetrance and expression, some females heterozygous for Fabry disease are symptomatic but not to the same degree as hemizygous males. The purpose of this study was to ascertain whether skewed X-inactivation favoring the mutant α-galactosidase A allele exists in our cohort of female heterozygotes of Fabry disease.

METHOD

All patients were evaluated by physical examination and ascribed disease-specific severity sub-scores for each of the four categories (cardiac, renal, neurological, general) and a total score using the Mainz Severity Score Index (MSSI). Blood samples were drawn for enzymatic activity of α-galactosidase A and for DNA extraction for analysis for α-galactosidase A mutations. XCI ratios were determined from peripheral blood leukocyte samples. The X-chromosome inactivation ratio was determined in each heterozygote.

RESULTS

Of 77 samples, only 18.2% were highly skewed (80/20). Only 14.3% of samples with nonsense mutations were highly skewed. There were no correlations between the XCI ratios and age, enzymatic activity of α-galactosidase A, MSSI sub-scores or total score, or with the clinical signs of cardiac involvement, neuropathic pain, or proteinuria.

CONCLUSION

These findings are comparable with others in Fabry disease, i.e., essentially the same as seen in normal non-elderly female population, raising the question of the mechanism underlying symptomatic phenotypic expression in heterozygous females with Fabry disease.

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.

Safety of agalsidase alfa in patients with Fabry disease under 7 years

AIM

To evaluate the safety and explore the efficacy of enzyme replacement therapy (ERT) for Fabry disease with agalsidase alfa in young children enrolled in the Fabry Outcome Survey (FOS).

METHODS

This retrospective chart review identified eight children (mean age= 5.0±1.6 [mean ±SD]) in FOS who began treatment with agalsidase alfa (0.2 mg/kg, i.v., every other week) when <7 years old. Vital signs and adverse events were monitored throughout the study period. Glomerular filtration rate (GFR) was estimated, and left ventricular mass indexed to height(2.7) (LVMi) was assessed with echocardiography. Patients received 1.2-6.7 years of treatment (mean=4.2 years).

RESULTS

Infusion reactions occurred in three patients and were of mild or moderate severity. IgG antibodies to agalsidase alfa were found in one patient who experienced two mild and one moderate infusion reactions. Mean GFR was within the normal range at baseline and remained normal. LVMi was above the 75th percentile of age-matched children in 5 of 6 patients evaluated at baseline. Only two patients exceeded this threshold at their last assessment.

CONCLUSION

Long-term observation will be needed to determine whether early initiation of ERT will prevent major organ dysfunction in these patients.

Update on role of agalsidase alfa in management of Fabry disease

Fabry disease (FD) is an X-linked lysosomal storage disorder that affects both men and women. The manifestations of this heterogeneous disease are multisystemic and progressive. Prior to the development of enzyme replacement therapy, the management and treatment for Fabry disease was largely nonspecific and supportive. Because enzyme replacement therapy became commercially available in 2001, a variety of clinical benefits in Fabry patients have been consistently reported, including improved renal pathology and cardiac function, and reduced severity of neuropathic pain and improved pain-related quality of life. This update focuses on published data on the efficacy and tolerability of enzyme replacement therapy with agalsidase alfa, and gives a brief overview on some of the outstanding management issues in the treatment of this complex disease.

Clinical practice: proteinuria

Proteinuria detection in children is a challenge. Five percent to 15% and 0.4-1% of school children present either transient (benign) or persistent increased amount of protein in urine, respectively. Persistent proteinuria constitutes not only a sign of overt kidney disease but may also be the first indicator of silent renal damage. Proteinuria is a marker for hyperfiltration in individuals with reduced nephron mass and one of the most important independent risk factor for renal disease progression as well. It constitutes the single most important risk factor for future loss of kidney function, preceding glomerular filtration rate reduction. Further, proteinuria itself is diagnostic of cardiovascular disease with prognostic value and target organ involvement in high-risk populations such as diabetic, obese, hypertensive children, or those with known reduced renal mass or previous renal injury. Current strategies to prevent CKD progression, a concept known as renoprotection, are focused on reducing urinary protein excretion among other factors. Reversibility of organ damage in early stages is possible; therefore, pediatricians should screen children for proteinuria or microalbuminuria, mainly in high-risk groups.

Fabry disease

Fabry disease (FD) is a progressive, X-linked inherited disorder of glycosphingolipid metabolism due to deficient or absent lysosomal α-galactosidase A activity. FD is pan-ethnic and the reported annual incidence of 1 in 100,000 may underestimate the true prevalence of the disease. Classically affected hemizygous males, with no residual α-galactosidase A activity may display all the characteristic neurological (pain), cutaneous (angiokeratoma), renal (proteinuria, kidney failure), cardiovascular (cardiomyopathy, arrhythmia), cochleo-vestibular and cerebrovascular (transient ischemic attacks, strokes) signs of the disease while heterozygous females have symptoms ranging from very mild to severe. Deficient activity of lysosomal α-galactosidase A results in progressive accumulation of globotriaosylceramide within lysosomes, believed to trigger a cascade of cellular events. Demonstration of marked α-galactosidase A deficiency is the definitive method for the diagnosis of hemizygous males. Enzyme analysis may occasionnally help to detect heterozygotes but is often inconclusive due to random X-chromosomal inactivation so that molecular testing (genotyping) of females is mandatory. In childhood, other possible causes of pain such as rheumatoid arthritis and 'growing pains' must be ruled out. In adulthood, multiple sclerosis is sometimes considered. Prenatal diagnosis, available by determination of enzyme activity or DNA testing in chorionic villi or cultured amniotic cells is, for ethical reasons, only considered in male fetuses. Pre-implantation diagnosis is possible. The existence of atypical variants and the availability of a specific therapy singularly complicate genetic counseling. A disease-specific therapeutic option - enzyme replacement therapy using recombinant human α-galactosidase A - has been recently introduced and its long term outcome is currently still being investigated. Conventional management consists of pain relief with analgesic drugs, nephroprotection (angiotensin converting enzyme inhibitors and angiotensin receptors blockers) and antiarrhythmic agents, whereas dialysis or renal transplantation are available for patients experiencing end-stage renal failure. With age, progressive damage to vital organ systems develops and at some point, organs may start to fail in functioning. End-stage renal disease and life-threatening cardiovascular or cerebrovascular complications limit life-expectancy of untreated males and females with reductions of 20 and 10 years, respectively, as compared to the general population. While there is increasing evidence that long-term enzyme therapy can halt disease progression, the importance of adjunctive therapies should be emphasized and the possibility of developing an oral therapy drives research forward into active site specific chaperones.