Different phenotypic expression in relatives with fabry disease caused by a W226X mutation

Detection of single nucleotide and copy number variants in the Fabry disease-associated GLA gene using nanopore sequencing

More than 900 variants have been described in the GLA gene. Some intronic variants and copy number variants in GLA can cause Fabry disease but will not be detected by classical Sanger sequence. We aimed to design and validate a method for sequencing the GLA gene using long-read Oxford Nanopore sequencing technology. Twelve Fabry patients were blindly analyzed, both by conventional Sanger sequence and by long-read sequencing of a 13 kb PCR amplicon. We used minimap2 to align the long-read data and Nanopolish and Sniffles to call variants. All the variants detected by Sanger (including a deep intronic variant) were also detected by long-read sequencing. One patient had a deletion that was not detected by Sanger sequencing but was detected by the new technology. Our long-read sequencing-based method was able to detect missense variants and an exonic deletion, with the added advantage of intronic analysis. It can be used as an efficient and cost-effective tool for screening and diagnosing Fabry disease.

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.

The coincidence of IgA nephropathy and Fabry disease

Background

IgA nephropathy (IgAN) is the most common glomerulonephritis, which may also coexist with other diseases. We present two patients with an unusual coincidence of IgAN and Fabry disease (FD).

Case presentation

A 26 year-old man underwent a renal biopsy in February 2001. Histopathology showed very advanced IgAN and vascular changes as a result of hypertension. Because of his progressive renal insufficiency the patient began hemodialysis in August 2001. By means of the blood spot test screening method the diagnosis of FD was suspected. Low activity of alpha-galactosidase A in the patient’s plasma and leukocytes and DNA analysis confirmed the diagnosis of FD. Enzyme replacement therapy started in July 2004. Then the patient underwent kidney transplantation in November 2005. Currently, his actual serum creatinine level is 250 μmol/l. Other organ damages included hypertrophic cardiomyopathy, neuropathic pain and febrile crisis. After enzyme replacement therapy, myocardial hypertrophy has stabilized and other symptoms have disappeared. No further progression of the disease has been noted.

The other patient, a 30 year-old woman, suffered from long-term hematuria with a good renal function. Recently, proteinuria (2.6 g/day) appeared and a renal biopsy was performed. Histopathology showed IgAN with remarkably enlarged podocytes. A combination of IgAN and a high suspicion of FD was diagnosed. Electron microscopy revealed dense deposits in paramesangial areas typical for IgAN and podocytes with inclusive zebra bodies and myelin figures characteristic of FD. FD was confirmed by the decreased alpha-galactosidase A activity in plasma and leukocytes and by DNA and RNA analysis. Enzyme replacement therapy and family screening were initiated.

Conclusions

Our results emphasize the role of complexity in the process of diagnostic evaluation of kidney biopsy samples. Electron microscopy represents an integral part of histopathology, and genetic analysis plays a more and more important role in the final diagnosis, which is followed by causal treatment.

Poikilothermia in a 38-year-old Fabry patient

A Fabry patient with poikilothermia is described. Laboratory investigations, neuro-imaging and autonomic function tests did not disclose a cause. Assessment of intra-epidermal nerve fibre density and quantitative sensory testing revealed small fibre neuropathy with a highly impaired cold sensation. We speculate that the poikilothermia is either caused by a vascular lesion in the hypothalamus not visible on MRI or by small fibre neuropathy leading to disturbed body temperature perception and therefore impaired thermoregulation.

Structure-function relationships in alpha-galactosidase A

With recent interest in the molecular mechanisms responsible for Fabry disease, the number of known mutations in the GLA gene which encodes alpha-galactosidase A has expanded considerably. Combining a large database of Fabry disease-causing mutations with the recently determined crystal structure of human alpha-galactosidase A allows for a new understanding of the atomic defects in the protein responsible for Fabry disease. We have conducted a systematic survey of the known Fabry disease-causing mutations and analyzed the mutations in the context of the alpha-galactosidase A structure. We have applied quantitative methods for identifying the plausible effect of each mutation on the alpha-galactosidase A protein. We present the analysis of 331 different defects in the GLA gene leading to non-native proteins in patients with Fabry disease. These mutations include 278 missense mutations, 49 nonsense mutations, and four single amino acid deletions.

CONCLUSION

Over half of the residues in the protein have been found to have changes in patients with Fabry disease. Most of these genetic mutations lead to disruption of the hydrophobic core of the protein, thus Fabry disease is primarily a disease of protein-folding. Further understanding of alpha-galactosidase A, one of the best studied members of the lysosomal storage disease family, will lead to increased understanding of other lysosomal storage diseases and other protein-folding diseases.

IgA nephropathy in two adolescent sisters heterozygous for Fabry disease

We report a 16-year-old girl and her one-year-younger sister, both heterozygous for the c.34del24 mutation of the GLA (alpha-galactosidase A) gene, which they inherited from their father who is affected by Fabry disease (FD). Both girls presented with macrohematuria and rapidly progressing proteinuria. Urine analysis revealed glomerular hematuria and a nephrotic range of proteinuria suggesting a concomitant glomerulonephritis. Light microscopy of kidney biopsy was characteristic of IgA nephropathy (IgA deposits in mesangial areas and glomerular capillary loops, and mesangial hypercellularity), whereas electron microscopy showed changes typical of Fabry disease (multiple osmiophilic inclusions in the subendothelial and mesangial areas). These two cases and similar reports in the literature suggest that IgA nephropathy in FD is not merely coincidental.

Single-gene mutations and increased left ventricular wall thickness in the community: the Framingham Heart Study

BACKGROUND

Mutations in sarcomere protein, PRKAG2, LAMP2, alpha-galactosidase A (GLA), and several mitochondrial genes can cause rare familial cardiomyopathies, but their contribution to increased left ventricular wall thickness (LVWT) in the community is unknown.

METHODS AND RESULTS

We studied 1862 unrelated participants (52% women; age, 59+/-9 years) from the community-based Framingham Heart Study who had echocardiograms and provided DNA samples but did not have severe hypertension, aortic prosthesis, or significant aortic stenosis. Eight sarcomere protein genes, 3 storage cardiomyopathy-causing genes, and 27 mitochondrial genes were sequenced in unrelated individuals with increased LVWT (maximum LVWT >13 mm). Fifty eligible participants (9 women) had unexplained increased LVWT. We detected 8 mutations in 9 individuals (2 women); 7 mutations in 5 sarcomere protein genes (MYH7, MYBPC3, TNNT2, TNNI3, MYL3), and 1 GLA mutation. In individuals with increased LVWT, participants with sarcomere protein and storage mutations were clinically indistinguishable from those without mutations.

CONCLUSIONS

In a community-based cohort, about 3% of eligible participants had increased LVWT, of whom 18% had sarcomere protein or lipid storage gene mutations. Increased LVWT in the community is a very heterogeneous condition, which sometimes may arise from single-gene variants in one of a number of genes.

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.

The expanding clinical spectrum of Anderson-Fabry disease: a challenge to diagnosis in the novel era of enzyme replacement therapy

Anderson-Fabry disease is an X-linked recessive lysosomal storage disease resulting from deficient alpha-galactosidase A activity. The conception of the disease has changed within the last decade. Studies of the last years have shown that the disease is not limited to the classical full-blown manifestation in affected males, which is well known since more than a century, but may also occur in carrier females. The phenomenology may differ in severity and kind of organ manifestation. Cardiac and renal variants with solely disease manifestation of these organs have also been described in an increasing number. It is likely that a spectrum exists regarding alpha-galactosidase A activity in both genders on the one hand, and an additional one regarding the severity and the number of organs affected on the other. The purpose of this review is to sharpen physicians' perception of this disease. Early and accurate diagnosis is mandatory considering that this disorder is now, after introduction of the novel enzyme replacement therapy, a treatable disease.

Anderson-Fabry disease: clinical manifestations of disease in female heterozygotes

Anderson-Fabry disease is a rare, X-chromosomal lipid storage disorder caused by a deficiency of lysosomal alpha-galactosidase A. Clinical manifestations of Anderson-Fabry disease include excruciating pain in the extremities (acroparaesthesia), skin vessel ectasia (angiokeratoma), corneal and lenticular opacity, cardiovascular disease, stroke and renal failure, only renal failure being a frequent cause of death. Heterozygote female carriers have often been reported as being asymptomatic or having an attenuated form of the disease. To evaluate the spectrum of clinical signs in heterozygotes, a comprehensive clinical examination was performed on 20 carriers of Anderson-Fabry disease. This revealed that, in addition to the skin manifestation, various other clinical manifestations of the disease are present, including acroparaesthesia, kidney dysfunction, cerebrovascular disease, and gastrointestinal and heart problems. It therefore appears that Anderson-Fabry disease affects both hemizygotes and heterozyotes and therefore should be considered to be an X-linked dominant disease.

Characterization of two alpha-galactosidase mutants (Q279E and R301Q) found in an atypical variant of Fabry disease

The mutant products Q279E ((279)Gln to Glu) and R301Q ((301)Arg to Gln) of the X-chromosomal inherited alpha-galactosidase (EC 3.2.1. 22) gene, found in unrelated male patients with variant Fabry disease (late-onset cardiac form) were characterized. In contrast to patients with classic Fabry disease, who have no detectable alpha-galactosidase activity, atypical variants have residual enzyme activity. First, the properties of insect cell-derived recombinant enzymes were studied. The K(m) and V(max) values of Q279E, R301Q, and wild-type alpha-galactosidase toward an artificial substrate, 4-methylumbelliferyl-alpha-D-galactopyranoside, were almost the same. In order to mimic intralysosomal conditions, the degradation of the natural substrate, globotriaosylceramide, by the alpha-galactosidases was analyzed in a detergent-free-liposomal system, in the presence of sphingolipid activator protein B (SAP-B, saposin B). Kinetic analysis revealed that there was no difference in the degradative activity between the mutants and wild-type alpha-galactosidase activity toward the natural substrate. Then, immunotitration studies were carried out to determine the amounts of the mutant gene products naturally occurring in cells. Cultured lymphoblasts, L-57 (Q279E) and L-148 (R301Q), from patients with variant Fabry disease, and L-20 (wild-type) from a normal subject were used. The 50% precipitation doses were 7% (L-57) and 10% (L-148) of that for normal lymphoblast L-20, respectively. The residual alpha-galactosidase activity was 3 and 5% of the normal level in L-57 and L-148, respectively. The quantities of immuno cross-reacting materials roughly correlated with the residual alpha-galactosidase activities in lymphoblast cells from the patients. Compared to normal control cells, fibroblast cells from a patient with variant Fabry disease, Q279E mutation, secreted only small amounts of alpha-galactosidase activity even in the presence of 10 mM NH(4)Cl. It is concluded that Q279E and R301Q substitutions do not significantly affect the enzymatic activity, but the mutant protein levels are decreased presumably in the ER of the cells.