A classical phenotype of Anderson-Fabry disease in a female patient with intronic mutations of the GLA gene: a case report

What Is Hidden in Patients with Unknown Nephropathy? Genetic Screening Could Be the Missing Link in Kidney Transplantation Diagnosis and Management

Between 15-20% of patients with end stage renal disease (ESRD) do not know the cause of the primary kidney disease and can develop complications after kidney transplantation. We performed a genetic screening in 300 patients with kidney transplantation, or undiagnosed primary renal disease, in order to identify the primary disease cause and discriminate between overlapping phenotypes. We used a custom-made panel for next-generation sequencing (Agilent technology, Santa Clara, CA, USA), including genes associated with Fabry disease, podocytopaties, complement-mediated nephropathies and Alport syndrome-related diseases. We detected candidate diagnostic variants in genes associated with nephrotic syndrome and Focal Segmental Glomerulosclerosis (FSGS) in 29 out of 300 patients, solving about 10% of the probands. We also identified the same genetic cause of the disease (PAX2: c.1266dupC) in three family members with different clinical diagnoses. Interestingly we also found one female patient carrying a novel missense variant, c.1259C>A (p.Thr420Lys), in the GLA gene not previously associated with Fabry disease, which is in silico defined as a likely pathogenic and destabilizing, and associated with a mild alteration in GLA enzymatic activity. The identification of the specific genetic background may provide an opportunity to evaluate the risk of recurrence of the primary disease, especially among patient candidates living with a donor kidney transplant.

Angiokeratoma corporis diffusum with severe acroparesthesia, an endothelial abnormality, and inconspicuous genetic findings

Angiokeratoma corporis diffusum (ACD) was long thought to be a specific dermal sign of Fabry disease (FD, X-linked alpha-galactosidase A [GLA] deficiency). However, other lysosomal storage diseases (LSDs) have also been identified as triggers of ACD. Generalized vasculopathy is an important pathogenetic factor in FD and may also lead to the acroparesthesia (AP) often predominant in FD. We report on an 85-year-old woman with ACD present since her youth and associated with severe AP. Ultrastructure of the dermal lesion showed no lysosomal involvement, but the absence of the basement membrane of the endothelial cells of the capillary vessels was noteworthy. Repeated analyses of the GLA gene revealed no evidence of FD. Whole-exome sequencing was negative for FD and other LSDs, and allowed us to also study FD-related intronic regions of the GLA gene. This is the first report of a patient with FD-like ACD with an endothelial abnormality, otherwise unexplained vasculopathy and severe AP, which are not due to FD or another LSD. Based on family history, another genetic, yet unidentified, defect may cause the disease in this patient. In unexplained ACD, extended genetic analysis is required to exclude particular pathogenic variants of the GLA gene and other genes.

Frequency of Fabry disease in a juvenile idiopathic arthritis cohort

BACKGROUND

Fabry disease (FD) is a rare, X-linked, multisystemic lysosomal storage disorder (LSD) that results from a deficiency in the hydrolase alpha-galactosidase A (⍺-GalA). During childhood, classic FD symptomatology is rare. The majority of children may show non-specific symptoms, including in the musculoskeletal system. The prevalence of FD among juvenile idiopathic arthritis (JIA) patients is unknown.

OBJECTIVE

This study aimed to identify the frequency of FD in a JIA cohort, characterizing early clinical symptoms, enzyme titers, and GLA genotyping.

METHODS

Children with JIA followed in a tertiary Children Hospital cohort were selected. Clinical, laboratory and familiar information were recorded. Molecular genetic testing to detect GLA gene mutations was performed in girls and enzymatic analysis in boys.

RESULTS

In 89 patients (56.2% female, age at disease onset: 8.93 ± 4.35 years), one male (1.12%) patient presented pathogenic mutation in GLA gene, c.1244 T > C p.L415P, one female patient had a variant of uncertain significance c.38C > T (p.Ala13Val). Three additional (3.4%) patients had the enzymatic activity of alpha-galactosidase slightly decreased. We observed the presence of intronic variants in 44.44% of patients in our cohort: c.1000-22C > T; c.370-81_-77del; c.640-16A > G; c.10C > T; c.548-125C > G and c.-12G > A. These variants and their combination were associated with clinical symptoms in our cohort.

CONCLUSIONS

The incidence of FD in our cohort was 1.12%. Intronic variants were associated with symptoms previously described in the literature. Screening for FD in JIA may be a reasonable strategy for those with an atypical pattern of pain.

Fabry Disease in Young Ischemic Stroke Patients in Northern Israel

INTRODUCTION

The prevalence of Fabry Disease (FD) with cerebrovascular complications varies in different populations. The aim of this study was to estimate the presence of FD among young stroke patients in northern Israel.

PATIENTS AND METHODS

We performed a retro-/prospective search for FD in young patients (aged ≤50 years old) admitted to the Department of Neurology due to acute ischemic stroke of any etiology.

RESULTS

Overall, 114 patients were examined for FD. Mean age of patients was 40±7.44 years. There were 75 (65.78%) males. FD was found in 4 (3.5%) patients. None of the FD patients had a cryptogenic stroke.

CONCLUSION

The results of our study call for a search of FD in young stroke patients of any etiology, and not only among cryptogenic ones.

Correlation between GLA variants and alpha-Galactosidase A profile in dried blood spot: an observational study in Brazilian patients

BACKGROUND

Fabry disease is a rare X-linked inherited disorder caused by deficiency of α-Galactosidase A. Hundreds of mutations and non-coding haplotypes in the GLA gene have been described; however, many are variants of unknown significance, prompting doubts about the diagnosis and treatment. The α-Galactosidase A enzymatic activity in dried blood spot (DBS) samples are widely used for screening purposes; however, even when values below the normal are found, new tests are required to confirm the diagnosis. Here we describe an analysis of GLA variants and their correlation with DBS α-Galactosidase A enzymatic activity in a large Brazilian population with Fabry disease symptoms.

RESULTS

We analyzed GLA variants by DNA sequencing of 803 male patients with suspected Fabry disease or belonging to high-risk populations; in 179 individuals, 58 different exonic variants were detected. From these, 50 are variants described as pathogenic and eight described as variants of unknown significance. The other individuals presented complex non-coding haplotypes or had no variants. Interestingly, the enzymatic activity in DBS was different among pathogenic variants and the other genotypes, including variants of unknown significance; the first presented mean of 12% of residual activity, while the others presented levels above 70% of the activity found in healthy controls.

CONCLUSION

The activity of α-Galactosidase A in DBS was markedly reduced in males with known pathogenic variants when compared with subjects presenting variants of unknown significance, non-coding haplotypes, or without variants, indicating a possible non-pathogenic potential of these latter genotypes. These findings bring a better understanding about the biochemical results of α-Galactosidase A in DBS samples, as well as the possible non-pathogenic potential of non-coding haplotypes and variants of unknown significance in GLA gene. These results certainly will help clinicians to decide about the treatment of patients carrying variants in the gene causing this rare but life-threatening disease.

Effectiveness of plasma lyso-Gb3 as a biomarker for selecting high-risk patients with Fabry disease from multispecialty clinics for genetic analysis

PURPOSE

Plasma globotriaosylsphingosine (lyso-Gb3) is a promising secondary screening biomarker for Fabry disease. Here, we examined its applicability as a primary screening biomarker for classic and late-onset Fabry disease in males and females.

METHODS

Between 1 July 2014 and 31 December 2015, we screened 2,359 patients (1,324 males) referred from 168 Japanese specialty clinics (cardiology, nephrology, neurology, and pediatrics), based on clinical symptoms suggestive of Fabry disease. We used the plasma lyso-Gb3 concentration, α-galactosidase A (α-Gal A) activity, and analysis of the α-Gal A gene (GLA) for primary and secondary screens, respectively.

RESULTS

Of 8 males with elevated lyso-Gb3 levels (≥2.0 ng ml-1) and low α-Gal A activity (≤4.0 nmol h-1 ml-1), 7 presented a GLA mutation (2 classic and 5 late-onset). Of 14 females with elevated lyso-Gb3, 7 displayed low α-Gal A activity (5 with GLA mutations; 4 classic and 1 late-onset) and 7 exhibited normal α-Gal A activity (1 with a classic GLA mutation and 3 with genetic variants of uncertain significance).

CONCLUSION

Plasma lyso-Gb3 is a potential primary screening biomarker for classic and late-onset Fabry disease probands.

Detection of blood Gb3 deposits as a new tool for diagnosis and therapy monitoring in patients with classic Fabry disease

BACKGROUND

The X-linked Fabry disease (FD) is a multiorgan disorder due to alpha-galactosidase A (α-GAL) deficiency with consequent lysosomal accumulation of globotriaosylceramide (Gb3). We established the immunocytochemical detection of Gb3 in blood cells of FD patients as a new method for FD diagnostics, follow-up and treatment control.

METHODS

We enrolled 67 FD patients (37 men, 30 women) and 52 healthy controls (26 men, 26 women). PBMC were isolated from whole venous blood and 3x10⁵ cells were immunoreacted with antibodies against CD77 as a marker for Gb3. Using fluorescence microscopy, the mean percentage of Gb3 positive PBMC was determined by an investigator blinded to subject allocation. As a second method, we qualitatively assessed Gb3 positive cells in blood smears.

RESULTS

Gb3 deposits were unequivocally visible in PBMC and in blood smears. Men (P < 0.001) and women (P < 0.01) with classical FD had more Gb3-positive PBMC than healthy controls, whose samples only occasionally showed positive cells. The number of Gb3 positive PBMC was negatively correlated with α-GAL activity and positively correlated with plasma lyso-Gb3 levels. Only the PBMC Gb3 load but not plasma lyso-Gb3 reflected short- and long-term effects of enzyme replacement therapy (P < 0.01).

CONCLUSIONS

Gb3 can be visualized in PBMC and blood smears and can be used as a novel marker for diagnostics, follow-up and treatment control in FD.

Fabry disease. A potential pitfall A family with a novel intronic mutation

Fabry disease is a genetic disorder characterized by the accumulation of globotriaosylceramide in cell lysosomes resulting from an X-linked deficiency of α-galactosidase A activity. It presents with multiorgan manifestations, including progressive renal disease, cardiomyopathy and premature demise. Recently, its prevalence has been reported to be higher in hemodialysis (HD) patients than in the general population. We report two cases of homozygous patients with an intronic alpha-galactosidase gene mutation and a classic phenotype of the disease. One of the patients had a kidney transplant and the donor was his brother, before Fabry disease were diagnose.

Restoring functional neurofibromin by protein transduction

In Neurofibromatosis 1 (NF1) germ line loss of function mutations result in reduction of cellular neurofibromin content (NF1+/-, NF1 haploinsufficiency). The Ras-GAP neurofibromin is a very large cytoplasmic protein (2818 AA, 319 kDa) involved in the RAS-MAPK pathway. Aside from regulation of proliferation, it is involved in mechanosensoric of cells. We investigated neurofibromin replacement in cultured human fibroblasts showing reduced amount of neurofibromin. Full length neurofibromin was produced recombinantly in insect cells and purified. Protein transduction into cultured fibroblasts was performed employing cell penetrating peptides along with photochemical internalization. This combination of transduction strategies ensures the intracellular uptake and the translocation to the cytoplasm of neurofibromin. The transduced neurofibromin is functional, indicated by functional rescue of reduced mechanosensoric blindness and reduced RasGAP activity in cultured fibroblasts of NF1 patients or normal fibroblasts treated by NF1 siRNA. Our study shows that recombinant neurofibromin is able to revert cellular effects of NF1 haploinsuffiency in vitro, indicating a use of protein transduction into cells as a potential treatment strategy for the monogenic disease NF1.

Fabry disease in the Spanish population: observational study with detection of 77 patients

Background

Fabry disease is a multisystemic lysosomal storage disorder caused by the impairment of α-galactosidase A. The incidence of this rare disease is underestimated due to delayed diagnosis. Moreover, the management of the identified subjects is often complicated by the detection of variants of unclear diagnostic interpretation, usually identified in screening studies. We performed an observational study based on biochemical and genetic analysis of 805 dried blood spot samples from patients with clinical symptoms or family history of this pathology, which were collected from 109 Spanish hospitals, all over the country.

Results

We identified 77 new diagnosed patients with mutations related to classical Fabry disease, as well as 2 subjects with c.374A > T; p.His125Leu, a possible new mutation that need to be confirmed. Additionally, we detected 8 subjects carrying genetic variants possibly linked to late onset Fabry disease (p.Arg118Cys and p.Ala143Thr), 4 cases with polymorphism p.Asp313Tyr and 36 individuals with single nucleotide polymorphisms in intronic regions of GLA. Five of the identified mutations (c.431delG; c.1182delA; c.374A > T; c.932 T > C; c.125 T > A; c.778G > A), which were associated with a classical phenotype have not been previously described. Moreover 3 subjects presenting complex haplotypes made up by the association of intronic variants presented impaired levels of GLA transcripts and Gb3 deposits in skin biopsy.

Conclusions

Enzymatic screening for Fabry Disease in risk population (2 or more clinical manifestations or family history of the disease) helped to identify undiagnosed patients and unravel the impairment of GLA expression in some subjects with complex haplotypes.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0792-8) contains supplementary material, which is available to authorized users.

Low frequency of Fabry disease in patients with common heart disease

PURPOSE

To test the hypothesis that undiagnosed patients with Fabry disease exist among patients affected by common heart disease.

METHODS

Globotriaosylceramide in random whole urine using tandem mass spectroscopy, α-galactosidase A activity in dried blood spots, and next-generation sequencing of pooled or individual genomic DNA samples supplemented by Sanger sequencing.

RESULTS

We tested 2,256 consecutive patients: 852 women (median age 65 years (19-95)) and 1,404 men (median age 65 years (21-92)). The primary diagnoses were coronary artery disease (n = 994), arrhythmia (n = 607), cardiomyopathy (n = 138), and valvular disease (n = 568). Urinary globotriaosylceramide was elevated in 15% of patients and 15 males had low α-galactosidase A activity. GLA variants found included R118C (n = 2), D83N, and D313Y (n = 7); IVS6-22 C>T, IVS4-16 A>G, IVS2+990C>A, 5'UTR-10 C>T (n = 4), IVS1-581 C>T, IVS1-1238 G>A, 5'UTR-30 G>A, IVS2+590C>T, IVS0-12 G>A, IVS4+68A>G, IVS0-10 C>T, IVS2-81-77delCAGCC, IVS2-77delC. Although the pathogenicity of several of these missense mutations and complex intronic haplotypes has been controversial, none of the patients screened in this study were diagnosed definitively with Fabry disease.

CONCLUSION

This population of patients with common heart disease did not contain a substantial number of patients with undiagnosed Fabry disease. GLA gene sequencing is superior to urinary globotriaosylceramide or α-galactosidase A activity in the screening for Fabry disease.

Identification of Cryptic Novel α-Galactosidase A Gene Mutations: Abnormal mRNA Splicing and Large Deletions

Anderson-Fabry (FD) disease is an inborn error of metabolism caused by a deficiency of α-galactosidase A (GLA), a lysosomal enzyme. Many male FD patients display a classic FD phenotype; however, some female patients have neither reduced leukocyte GLA enzyme activity level nor FD symptoms. Thus, GLA gene analysis is especially important for diagnosing suspected FD in female subjects. In this study, we revealed 4 novel GLA gene mutations in 5 independent families using GLA cDNA analysis and multiplex ligation-dependent probe amplification (MLPA) analysis. These distinct mutations included a large deletion mutation from intron 1 to exon 5 (c.195-471_c.691del5.5k, corresponding to g.8508_g.14069del5.5k), an insertion mutation of splicing enhancer sequence in intron 4 (c.639+329_c.639+330ins113, corresponding to g.12627_g.12628ins113), an insertion mutation of retrotransposon L1 in exon 4 (c.634_c.635, corresponding to g.12293_g.12294), and a non-SNP deep intronic point mutation in intron 3 (c.547+395G>C, corresponding to g.11727G>C). It is difficult to detect these mutations with direct sequencing of only the exonic element. When exonic mutations are not found in the GLA gene from suspected FD patients, GLA cDNA and MLPA analyses should be performed to detect large deletion/insertion and intronic mutations including transcription abnormalities.

Increased glycolipid storage produced by the inheritance of a complex intronic haplotype in the α-galactosidase A (GLA) gene

Background

Accumulation of galactosphingolipids is a general characteristic of Fabry disease, a lysosomal storage disorder caused by the deficient activity of α-galactosidase A encoded by the GLA gene. Although many polymorphic GLA haplotypes have been described, it is still unclear whether some of these variants are causative of disease symptoms. We report the study of an inheritance of a complex intronic haplotype (CIH) (c.-10C > T, c.369 + 990C > A, c.370-81_370-77delCAGCC, c.640-16A > G, c.1000-22C > T) within the GLA gene associated with Fabry-like symptoms and galactosphingolipid accumulation.

We analysed α-Gal A activity in plasma, leukocytes and skin fibroblasts in patients, and measured accumulation of galactosphingolipids by enzymatic methods and immunofluorescence techniques. Additionally, we evaluated GLA expression using quantitative PCR, EMSA, and cDNA cloning.

Results

CIH carriers had an altered GLA expression pattern, although most of the carriers had high residual enzyme activity in plasma, leukocytes and in skin fibroblasts. Nonetheless, CIH carriers had significant galactosphingolipid accumulation in fibroblasts in comparison with controls, and also glycolipid deposits in renal tubules and glomeruli. EMSA assays indicated that the c.-10C > T variant in the promoter affected a nuclear protein binding site.

Conclusions

Thus, inheritance of the CIH caused an mRNA deregulation altering the GLA expression pattern, producing a tissue glycolipid storage.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0267-z) contains supplementary material, which is available to authorized users.

Cryptogenic stroke and small fiber neuropathy of unknown etiology in patients with alpha-galactosidase A -10T genotype

BACKGROUND

Fabry disease (FD) is a multisystemic disorder with typical neurological manifestations such as stroke and small fiber neuropathy (SFN), caused by mutations of the alpha-galactosidase A (GLA) gene. We analyzed 15 patients carrying the GLA haplotype -10C>T [rs2071225], IVS2-81_-77delCAGCC [rs5903184], IVS4-16A>G [rs2071397], and IVS6-22C>T [rs2071228] for potential neurological manifestations.

METHODS AND RESULTS

Patients were retrospectively analyzed for stroke, transient ischemic attack (TIA), white matter lesions (WML) and SFN with neuropathic pain. Functional impact of the haplotype was determined by molecular genetic methods including real-time PCR, exon trapping, promoter deletion constructs and electrophoretic mobility shift assays. Symptomatic -10T allele carriers suffered from stroke, TIA, WML, and SFN with neuropathic pain. Patients' mean GLA mRNA expression level was reduced to ~70% (p < 0.0001) and a dose-dependent effect of the -10T allele on GLA mRNA expression was observed in hemi/homozygous compared to heterozygous patients (p < 0.0001). Molecular analyzes revealed that the -10T allele resulted in a reduced promoter activity and an altered transcription factor binding, while a functional relevance of the co-segregated intronic variants was excluded by exon trapping.

CONCLUSIONS

Based on this complementary approach of clinical observation and functional testing, we conclude that the GLA -10T allele could be causal for the observed neurological manifestations. Future studies are needed to clarify whether affected patients benefit from GLA enzyme replacement therapy for end-organ damage prevention.

An intronic haplotype in α galactosidase A is associated with reduced mRNA expression in males with cryptogenic stroke

Persons with unexplained early-onset stroke have been targeted for screening surveys for Fabry disease, the most common of the three X-linked lysosomal disorders, because Fabry patients with stroke are more likely to have the life-threatening progressive cardiac and renal manifestations and would therefore most benefit from early diagnosis and intervention with enzyme replacement therapy (ERT). Among 175 Israeli patients with unexplained cryptogenic stroke screened for mutations in the Fabry α galactosidase A (GLA) gene, sequencing identified six with 2-4 GLA intronic variants, one of whose father and three sisters had the same variants. Two variants, c.640-16A>G (g.10115A>G) in intron 4 and c.1000-22C>T (g.10956C>T) in intron 6, were common to all patients. However, three males with a common four variant intronic haplotype had low residual enzyme activity and ~50% reduced mRNA expression. Transcript splice-site defects were not identified in any of the index cases and X-chromosome inactivation was not highly skewed in the six females. These data do not suggest that GLA intronic variants, per se, are pathogenic. Nonetheless, it is clear that a certain intronic haplotype in males with cryptogenic stroke is associated with reduced GLA expression and function.