Mutational spectrum and genotype-phenotype correlation in Mexican patients with infantile-onset and late-onset Pompe disease.

BACKGROUND: Pompe Disease (PD) is a metabolic myopathy caused by variants in the GAA gene, resulting in deficient enzymatic activity. We aimed to characterize the clinical features and related genetic variants in a series of Mexican patients. METHODS: We performed a retrospective study of clinical records of patients diagnosed with LOPD, IOPD or pseudodeficiency. RESULTS: Twenty-nine patients were included in the study, comprising these three forms. Overall, age of symptom onset was 0.1 to 43 years old. The most frequent variant identified was c.-32-13T>G, which was detected in 14 alleles. Among the 23 different variants identified in the GAA gene, 14 were classified as pathogenic, 5 were likely pathogenic, and 1 was a variant of uncertain significance. Two variants were inherited in cis arrangement and 2 were pseudodeficiency-related benign alleles. We identified two novel variants (c.1615 G>A and c.1076-20_1076-4delAAGTCGGCGTTGGCCTG). CONCLUSION: To the best of our knowledge, this series represent the largest phenotypic and genotypic characterization of patients with PD in Mexico. Patients within our series exhibited a combination of LOPD and IOPD associated variants, which may be related to genetic diversity within Mexican population. Further population-wide studies are required to better characterize the incidence of this disease in Mexican population.

Novel Mutation in the Feline GAA Gene in a Cat with Glycogen Storage Disease Type II (Pompe Disease).

Glycogen storage disease type II (Pompe disease: PD) is an autosomal recessively inherited fatal genetic disorder that results from the deficiency of a glycogen hydrolyzing enzyme, acid α-glucosidase encoded by the GAA gene. Here, we describe the molecular basis of genetic defects in an 8-month-old domestic short-haired cat with PD. The cat was previously diagnosed with PD based on the clinical and pathological findings of hypertrophic cardiomyopathy and excessive accumulation of glycogen in the cardiac muscles. Sanger sequencing was performed on 20 exons of the feline GAA gene using genomic DNA extracted from paraffin-embedded liver tissues. The affected cat was found to be homozygous for the GAA:c.1799G>A mutation resulting in an amino acid substitution (p.R600H) of acid α-glucosidase, a codon position of which is identical with three missense mutations (p.R600C, p.R600L, and p.R600H) causing human infantile-onset PD (IOPD). Several stability and pathogenicity predictors have also shown that the feline mutation is deleterious and severely decreases the stability of the GAA protein. The clinical, pathological, and molecular findings in the cat were similar to those of IOPD in humans. To our knowledge, this is the first report of a pathogenic mutation in a cat. Feline PD is an excellent model for human PD, especially IOPD.

[Research progress of nervous system damage in Pompe disease]. / åºžè´ç— ç¥žç»ç³»ç»ŸæŸä¼¤çš„ç ”ç©¶è¿›å±•.

Pompe disease, also known as glycogen storage disease type Ⅱ, is a rare autosomal recessive disease. With the application of enzyme replacement therapy, more and more patients with Pompe disease can survive to adulthood, and nervous system-related clinical manifestations gradually emerge. Nervous system involvement seriously affects the quality of life of patients with Pompe disease, and a systematic understanding of the clinical manifestations, imaging features and pathological changes of nervous system injury in Pompe disease is of great significance for the early identification and intervention of Pompe disease. This article reviews the research progress of neurological damage in Pompe disease.

Infantile-onset Pompe disease with neutropenia: Treatment decisions in the face of a unique phenotype.

Infantile-onset Pompe disease manifests with early signs of cardiomyopathy during the first few days to weeks of life. We present the case of a newborn born via emergency cesarean section with atrial flutter and moderate biventricular hypertrophy who was diagnosed with Pompe disease on New York State newborn screen. Diagnosis was confirmed with repeat leukocyte acid alpha-glucosidase (GAA) enzyme activity, GAA gene sequencing, urine Hex4, and evaluation of Cross-Reactive Immunological Material (CRIM) status. The patient was also found to be persistently neutropenic which to our knowledge has not been previously reported in the literature in association with Pompe disease. This report highlights the impact that newborn screening had on time to diagnosis and initiation of treatment with enzyme replacement therapy. We also discuss how our patient's concurrent neutropenia impacted decision making related to immune tolerance induction prior to starting enzyme replacement therapy.

Research progress of nervous system damage in Pompe disease / 中国当代儿科杂志

Pompe disease, also known as glycogen storage disease type Ⅱ, is a rare autosomal recessive disease. With the application of enzyme replacement therapy, more and more patients with Pompe disease can survive to adulthood, and nervous system-related clinical manifestations gradually emerge. Nervous system involvement seriously affects the quality of life of patients with Pompe disease, and a systematic understanding of the clinical manifestations, imaging features and pathological changes of nervous system injury in Pompe disease is of great significance for the early identification and intervention of Pompe disease. This article reviews the research progress of neurological damage in Pompe disease.

Retrospective analysis of prenatal ultrasound of children with Pompe disease.

OBJECTIVE: The aim of this retrospective study is to determine the prenatal ultrasound markers of patients diagnosed postnatally with infantile-onset Pompe disease (IOPD). MATERIALS AND METHODS: This is a retrospective study of cases with a postnatal diagnosis of IOPD during a 5-year period. The medical file of the patients with IOPD was reviewed, and data regarding especially pregnancy were collected. RESULTS: Second trimester fetal sonographic anatomical scan was performed in all 13 cases during pregnancy. Two cases (15.4%) were found to have a persistently open mouth at 23 weeks and 24 weeks, respectively. Serials follow-up ultrasound examinations demonstrated the same findings in the two cases. Third trimester ultrasound was also performed in all cases. Large heart was found in five cases (38.5%), and fetal echocardiography confirmed hypertrophic cardiomyopathy. CONCLUSION: Our results indicate that a mid-trimester open mouth and third-trimester hypertrophic cardiomyopathy are the prenatal findings associated with the disorder of IOPD.

Genotypic and phenotypic characteristics of 12 chinese children with glycogen storage diseases.

Background: Glycogen storage diseases (GSDs) are known as a group of disorders characterized by genetic errors leading to accumulation of glycogen in various tissues. Since different types of GSD can sometimes be clinically indistinguishable, next generation sequencing is becoming a powerful tool for clinical diagnosis. Methods: 12 patients with suspected GSDs and their parents were enrolled in this study. The clinical and laboratory data of the patients were reviewed. Causative gene variants were identified in the patients using whole exome sequencing (WES) and verified by Sanger sequencing. Results: Genetic testing and analysis showed that 7 patients were diagnosed with GSD II (Pompe disease), 2 patients with GSD III, 1 patient with GSD VI, and 2 patients with GSD IXα. A total number of 18 variants were identified in 12 patients including 11 variants in GAA gene, 3 variants in AGL gene, 2 variants in PYGL gene and 2 variants in PHKA2 gene, of which 9 variants were reported and 9 variants were novel. SIFT, Polyphen-2, Mutation Taster, and REVEL predicted the novel variants (except GAA c.1052_1075 + 47del) to be disease-causing. The 3D structures of wild/mutant type GAA protein were predicted indicating that variants p. Trp621Gly, p. Pro541Leu, p. Ser800Ile and p. Gly293Trp might affect the proteins function via destroying hydrogen bonds or conformational constraints. Neither liver size nor laboratory findings allow for a differentiation among GSD III, GSD VI and GSD IXα. Conclusion: Our study expanded the variation spectrum of genes associated with GSDs. WES, in combination with clinical, biochemical, and pathological hallmarks, could provide accurate results for diagnosing and sub-typing GSD and related diseases in clinical setting.

A favorable outcome in an infantile-onset Pompe patient with cross reactive immunological material (CRIM) negative disease with high dose enzyme replacement therapy and adjusted immunomodulation.

Infantile onset Pompe disease (IOPD) is a rare devastating disease that presents in early infancy with rapidly progressive hypertrophic cardiomyopathy, severe generalized myopathy and death within the first year of life. The emergence of enzyme replacement therapy (ERT) with recombinant human acid alpha glucosidase (rhGAA) has improved the natural course of IOPD with a significant impact on cardiomyopathy but has a more limited effect on the progression of myopathy and consequently the later deterioration of the disease. Possible reasons for reduced ERT efficacy include insufficient enzyme, partial targeting of skeletal muscle and the development of IgG rhGAA antibodies especially in patients who are cross-reactive immunological material (CRIM) negative. We report a CRIM-negative IOPD female patient who started treatment upon diagnosis at 4.5 months with ERT at 20 mg/kg every other week and a course of combined immunomodulation with rituximab, methotrexate and IVIG according to the published Duke protocol and increased ERT within a month to 40 mg/kg/week. Despite initial good clinical response to ERT and immunomodulation, monthly monitoring identified a gradual increase of serum antibody titers to rhGAA necessitating a second course of immunomodulation with bortezomib and maintenance rituximab and methotrexate. A gradual reduction in frequency of immunotherapy was instituted and over a period of 14 months was discontinued. Serum anti-rhGAA antibody titers remained negative for 5 months since cessation of immunomodulation and the patient is now immune tolerant with recovery of CD19. At the age of 30 months the patient is walking independently and has normal cardiac function and anatomy. We recommend initiating ERT at 40 mg/kg/week in CRIM-negative IOPD patients, concomitant with immunomodulation and monthly monitoring of serum anti-rhGAA IgG titers upon confirmation of the diagnosis.

Classic infantile-onset Pompe disease with histopathological neurologic findings linked to a novel GAA gene 4 bp deletion: A case study.

Pompe disease (PD) is an autosomal recessive disorder by a deficiency of acid α-glucosidase (GAA) with intralysosomal glycogen accumulation in multiple tissues. We present the case of a 5-month-old male with hypertrophic cardiomyopathy, hypotony, feeding difficulties, and oxygen requirement since birth. At 3 months of age, he develops heart failure, respiratory impairment, and neurological deterioration. The echocardiogram revealed concentric hypertrophic cardiomyopathy with left-diastolic dysfunction. We found increased creatine-phosphokinase, lactate dehydrogenase, and urinary glucose tetrasaccharide levels, 50% of PAS-positive vacuolated lymphocytes in the peripheral blood smear, and low GAA activity. Sequencing of coding exons and flanking intronic sequences revealed a novel homozygous 4 bp deletion in exon 15 of the GAA gene (c.2066_2069delAGCC/p.Glu689Glyfs*6). IOPD was diagnosed. At 5 months old, we started enzyme replacement therapy with an alpha-alglucosidase of 20 mg/kg weekly and immunomodulation with intravenous immunoglobulin. He developed two cardiorespiratory arrests with subsequent neurologic deterioration, convulsive crisis, and respiratory failure and died at 9 months old. We found the usual PD hallmarks in the heart, striated muscle, and liver but also we found neuronal lesions characterized by cytoplasm vacuolization with PAS-positive granules in the central nervous system and myenteric plexus. We describe a novel GAA gene pathogenic variant with a particular phenotype characterized by classic IOPD and neurologic histopathological findings. Enhancing the knowledge of lysosomal diseases is critical to improving the diagnosis and treatment of these patients.

Two Approaches for a Genetic Analysis of Pompe Disease: A Literature Review of Patients with Pompe Disease and Analysis Based on Genomic Data from the General Population.

In this study, two different approaches were applied in the analysis of the GAA gene. One was analyzed based on patients with Pompe disease, and the other was analyzed based on GAA genomic data from unaffected carriers in a general population genetic database. For this, GAA variants in Korean and Japanese patients reported in previous studies and in patients reported in the Pompe disease GAA variant database were analyzed as a model. In addition, GAA variants in the Korean Reference Genome Database (KRGDB), the Japanese Multi Omics Reference Panel (jMorp), and the Genome Aggregation Database (gnomAD) were analyzed. Overall, approximately 50% of the pathogenic or likely pathogenic variants (PLPVs) found in unaffected carriers were also found in real patients with Pompe disease (Koreans, 57.1%; Japanese, 46.2%). In addition, there was a moderate positive correlation (Spearman's correlation coefficient of 0.45-0.69) between the proportion of certain PLPVs in patients and the minor allele frequency of their variants in a general population database. Based on the analysis of general population databases, the total carrier frequency for Pompe disease in Koreans and Japanese was estimated to be 1.7% and 0.7%, respectively, and the predicted genetic prevalence was 1:13,657 and 1:78,013, respectively.

Genotype-phenotype correlation of 17 cases of Pompe disease in Spanish patients and identification of 4 novel GAA variants.

BACKGROUND: Pompe disease (PD) is an autosomal recessive metabolic disorder caused by pathogenic variants in the acid α-glucosidase gene (GAA) that produces defects in the lysosomal acid α-1,4-glucosidase. We aimed to identify genetic variations and clinical features in Spanish subjects to establish genotype-phenotype correlation. METHODS: A total of 2637 samples of patients who showed symptoms or susceptible signs of PD were enrolled in this observational study. Enzymatic activity was detected by fluorometric techniques and the genetic study was carried out using Next-Generation Sequencing. RESULTS: Fourteen different variants from 17 diagnosed patients were identified, seven males and nine females with LOPD (mean age 36.07, SD 20.57, range 7-64) and a 2-day-old boy with IOPD, four genetic variants had not been described in the literature previously, including a homozygous variant. In all of them α-glucosidase activity was decreased. Muscle weakness, respiratory distress, exercise intolerance, hypotonia, dysphagia and myalgia were commonly observed in patients. CONCLUSIONS: This study report four new genetic variants that contribute to the pathogenic variants spectrum of the GAA gene. We confirm that patients in Spain have a characteristic profile of a European population, with c.-32-13T>G being the most prevalent variant. Furthermore, it was confirmed that the c.236_246delCCACACAGTGC pathogenic variant in homozygosity is associated with early disease and a worse prognosis.

GAA gene mutation detection following clinical evaluation and enzyme activity analysis in Azeri Turkish patients with Pompe disease.

Pompe disease (PD) is a rare autosomal recessive multi-systemic lysosomal storage disorder, caused by mutations in the acid alpha-glucosidase (GAA) gene located on 17q25.2-q25.3. It is one of about 50 rare genetic diseases categorized as lysosomal storage disorders. This disease is characterized by a range of different symptoms related to acid alpha-glucosidase deficiency. Mutation recognition in the GAA gene can be very significant for purposes such as therapeutic interference, early diagnosis and genotype-phenotype relationship. In the current study, peripheral blood samples were gathered from patients with PD and healthy members of three families. Enzymatic activity of GAA was checked. Then, mutation detection was performed by polymerase chain reaction followed by direct sequencing of all exons in samples with decreased enzyme activity. The identified mutations were investigated using bioinformatics tools to predict possible effects on the protein product and also to compare the mutated sequence with near species. Three novel mutations (c.1966-1968delGAG, c.2011-2012delAT and c.1475-1481dupACCCCAC) were identified in the GAA gene. Assessment of the effects of these mutations on protein structure and function showed the possibility of harmful effects and their significant alterations in the protein structure. The three novel GAA gene mutations detected in this study expand the information about the molecular genetics of PD and can be used to helpdiagnosis and genetic counseling of affected families.

Mutations in GAA Gene in Tunisian Families with Infantile Onset Pompe Disease: Novel Mutation and Structural Modeling Investigations.

Pompe disease, a rare, autosomal, recessive, inherited, lysosomal storage disorder, is caused by mutations in the acid α-glucosidase (GAA) gene leading to a deficiency of the lysosomal GAA enzyme. Some GAA mutations eliminate all enzymatic activities, causing severe infantile Pompe disease; others allow residual GAA activity and lead to middle adulthood forms. Here, we report a cohort of 12 patients, belonging to 11 unrelated families, with infantile Pompe disease. The mutational analysis of GAA gene revealed a novel c.1494G > A (p.Trp498X) mutation in one patient and three known mutatio,ns including the c.1497G > A (p.Trp499X) mutation, in two patients, the c.1927G > A (p.Gly643Arg) mutation in one patient and the common c.236_246del (p.Pro79ArgfsX13) mutation in eight patients. The high prevalence of c.236_246del mutation in our cohort (58%) was supported by the existence of a common founder ancestor that was confirmed by its segregation of similar SNPs haplotype, including four intragenic SNPs of GAA gene. In addition, a 3D structure model and a docking were generated for the mutant p.Gly643Arg using the crystal structure of human GAA as template and the 4-methylumbelliferyl-α-D-glucopyranoside as substrate. The results showed that the arginine at position 643 caused electrostatic changes in neighboring regions, leading to the repulsion between the amino acids located in the catalytic cavity of the GAA enzyme, thus restricting access to its substrate. These structural defects could cause the impairment of the transport and maturation previously reported for p.Gly643Arg mutation.

Characterization of immune response in Cross-Reactive Immunological Material (CRIM)-positive infantile Pompe disease patients treated with enzyme replacement therapy.

Enzyme replacement therapy (ERT) with rhGAA has improved clinical outcomes in infantile Pompe disease (IPD). A subset of CRIM-positive IPD patients develop high and sustained antibody titers (HSAT; ≥51,200) and/or sustained intermediate titer (SIT; ≥12,800 and <51,200), similar to CRIM-negative patients. To date there has been no systematic study to analyze the extent of IgG antibody response in CRIM-positive IPD. Such data would be critical and could serve as a comparator group for potential immune modulation approaches. A retrospective analysis of the dataset from the original rhGAA clinical trials final reports was conducted. CRIM-positive patients who received ERT monotherapy and had >6 months of antibody titer data available, were included in the study. Patients were classified based on their longitudinal antibody titers into HSAT, SIT, and low titer (LT; <12,800) groups. Of the 37 patients that met inclusion criteria, five (13%), seven (19%), and 25 (68%) developed HSAT, SIT, and LT, respectively. Median peak titers were 204,800 (51,200-409,600), 25,600 (12,800-51,200), and 800 (200-12,800) for HSAT, SIT, and LT groups, respectively. Median last titers were 102,400 (51,200-409,600), 1600 (200-25,600), and 400 (0-12,800) at median time since ERT initiation of 94 weeks (64-155 weeks), 104 weeks (86-144 weeks), and 130 weeks (38-182 weeks) for HSAT, SIT, and LT groups, respectively. 32% (12/37) of CRIM-positive IPD patients developed HSAT/SIT which may lead to limited ERT response and clinical decline. Further Studies are needed to identify CRIM-positive IPD patients at risk of developing HSAT/SIT, especially with the addition of Pompe disease to the newborn screening.

Post-mortem diagnosis of Pompe disease by exome sequencing in a Moroccan family: a case report.

BACKGROUND: Pompe disease is an autosomal recessive lysosomal storage disorder characterized by progressive myopathy with proximal muscle weakness, respiratory muscle dysfunction, and cardiomyopathy. Its prevalence ranges between 1/9000 and 1/40,000. It is caused by compound heterozygous or homozygous mutations in the GAA gene, which encodes for the lysosomal enzyme alpha-glucosidase, required for the degrading of lysosomal glycogen. CASE PRESENTATION: In this study, we report the case of a Moroccan consanguineous family with hypertrophic cardiomyopathy and sudden cardiac deaths at an early age; our patient was a 7-month-old Moroccan girl. Whole exome sequencing identified the deleterious homozygous mutation c.236_246delCCACACAGTGC (p.Pro79ArgfsX13) of GAA gene leading to a post-mortem diagnosis of Pompe disease. CONCLUSION: The identification of the genetic substrate in our patient, the daughter, confirmed the clinical diagnosis of Pompe disease and allowed us to provide appropriate genetic counseling to the family for future pregnancies.

Glycogen Reduction in Myotubes of Late-Onset Pompe Disease Patients Using Antisense Technology.

Glycogen storage disease type II (GSDII) is a lysosomal disorder caused by the deficient activity of acid alpha-glucosidase (GAA) enzyme, leading to the accumulation of glycogen within the lysosomes. The disease has been classified in infantile and late-onset forms. Most late-onset patients share a splicing mutation c.-32-13T > G in intron 1 of the GAA gene that prevents efficient recognition of exon 2 by the spliceosome. In this study, we have mapped the splicing silencers of GAA exon 2 and developed antisense morpholino oligonucleotides (AMOs) to inhibit those regions and rescue normal splicing in the presence of the c.-32-13T > G mutation. Using a minigene approach and patient fibroblasts, we successfully increased inclusion of exon 2 in the mRNA and GAA enzyme production by targeting a specific silencer with a combination of AMOs. Most importantly, the use of these AMOs in patient myotubes results in a decreased accumulation of glycogen. To our knowledge, this is the only therapeutic approach resulting in a decrease of glycogen accumulation in patient tissues beside enzyme replacement therapy (ERT) and TFEB overexpression. As a result, it may represent a highly novel and promising therapeutic line for GSDII.

Late-onset pompe disease in Iran: A clinical and genetic report.

INTRODUCTION: Pompe disease is characterized by absence or deficiency of acid α-glucosidase, and several causative mutations are known. In this study we report clinical and laboratory data in Iranian patients with late-onset Pompe disease (LOPD), focusing on population-specific mutations. METHODS: Clinical and laboratory data of 14 patients from 10 families with the diagnosis of LOPD were recorded. All had reduced enzyme activity on dried blood spot (DBS) analysis. Genetic investigation was performed to identify the underlying mutations. RESULTS: The age of onset ranged from <2 to 38 years. The clinical presentations were heterogeneous. Two siblings presented with foot drop. The most common mutation was c.(-32-13T>G). There were 4 novel mutations: c.(2040 + 2dup); c.(1650delG); c.(1837T>G); and c.(2596delG). CONCLUSION: This is a comprehensive report of LOPD in Iranian patients. Distinct phenotypic and genotypic features in this population are highlighted. Muscle Nerve 55: 835-840, 2017.

Guidelines for the diagnosis, treatment and clinical monitoring of patients with juvenile and adult Pompe disease / Diretriz para o diagnóstico, tratamento e acompanhamento clínico de pacientes com doença de Pompe juvenil e do adulto

ABSTRACT Pompe disease (PD) is a potentially lethal illness involving irreversible muscle damage resulting from glycogen storage in muscle fiber and activation of autophagic pathways. A promising therapeutic perspective for PD is enzyme replacement therapy (ERT) with the human recombinant enzyme acid alpha-glucosidase (Myozyme®). The need to organize a diagnostic flowchart, systematize clinical follow-up, and establish new therapeutic recommendations has become vital, as ERT ensures greater patient longevity. A task force of experienced clinicians outlined a protocol for diagnosis, monitoring, treatment, genetic counseling, and rehabilitation for PD patients. The study was conducted under the coordination of REBREPOM, the Brazilian Network for Studies of PD. The meeting of these experts took place in October 2013, at L’Hotel Port Bay in São Paulo, Brazil. In August 2014, the text was reassessed and updated. Given the rarity of PD and limited high-impact publications, experts submitted their views.

RESUMO A doença de Pompe (DP) é uma doença grave, potencialmente letal, devida ao depósito de glicogênio na fibra muscular e ativação de vias autofágicas. Tratamento promissor para a DP é a reposição enzimática com a enzima recombinante humana alfa-glicosidase ácida (rhAGA -Myozyme®). A necessidade de organizar uma propedêutica diagnóstica, sistematizar o seguimento clínico e sedimentar as novas recomendações terapêuticas tornaram-se vitais à medida que o tratamento permite uma maior longevidade aos pacientes. Uma força-tarefa de clínicos experientes no manejo da DP foi constituída para elaborar um protocolo para o diagnóstico, acompanhamento clínico, tratamento, aconselhamento genético, entre outras considerações voltadas ao paciente adulto. O estudo foi realizado sob a coordenação da Rede Brasileira de Estudos da Doença de Pompe (REBREPOM). Diante da raridade da DP e escassez de trabalhos de alto impacto de evidência científica, os especialistas emitiram suas opiniões.

Late onset form of Pompe disease.

BACKGROUND: Pompe disease is an autosomal recessive disorder of glycogen metabolism caused by deficiency in lysosomal enzyme α-glucosidase. OBJECTIVES: We present first two patients from Slovakia with confirmed Pompe disease. METHODS: Activity of α-glucosidase was measured using 4-methylumbelliferyl-α-D-glucopyranoside with the presence of acarbose, inhibitor that eliminates isoenzyme interference of maltase-glucoamylase. This methodical approach is substantial for determination of lysosomal enzyme deficiency. Using molecular genetic methods, PCR-RFLP and direct sequencing of coding region α-glucosidase gene (GAA) we have identified causal mutations in our patients. RESULTS: Late-onset type of disease was confirmed by measuring α-glucosidase activity in leukocytes isolated from blood. The presence of common Caucasian mutation c.-32-13T>G was proved by genetic testing in the first patient in homozygous state. Second patient was a compound heterozygote, with mutation c.-32-13T>G on one allele and mutation A486P on the second allele. CONCLUSION: We present a diagnostic algorithm for diagnosing the Pompe disease in patients of European origin. Enzyme replacement therapy has been used as a treatment option for improving the quality of life of patients. Early diagnosis and treatment of Pompe disease are considered to be critical for maximum efficacy of enzyme replacement therapy (Tab. 1, Fig. 3, Ref. 20).

Novel GAA mutations in patients with Pompe disease.

Pompe disease is an autosomal recessive disorder linked to GAA gene that leads to a multi-system intralysosomal accumulation of glycogen. Mutation identification in the GAA gene can be very important for early diagnosis, correlation between genotype-phenotype and therapeutic intervention. For this purpose, peripheral blood from 57 individuals susceptible to Pompe disease was collected and all exons of GAA gene were amplified; the sequences and the mutations were analyzed in silico to predict possible impact on the structure and function of the human protein. In this study, 46 individuals presented 33 alterations in the GAA gene sequence, among which five (c.547-67C>G, c.547-39T>G, p.R437H, p.L641V and p.L705P) have not been previously described in the literature. The alterations in the coding region included 15 missense mutations, three nonsense mutations and one deletion. One insertion and other 13 single base changes were found in the non-coding region. The mutation p.G611D was found in homozygosis in a one-year-old child, who presented low levels of GAA activity, hypotonia and hypertrophic cardiomyopathy. Two patients presented the new mutation p.L705P in association with c.-32-13T>G. They had low levels of GAA activity and developed late onset Pompe disease. In our study, we observed alterations in the GAA gene originating from Asians, African-Americans and Caucasians, highlighting the high heterogeneity of the Brazilian population. Considering that Pompe disease studies are not very common in Brazil, this study will help to better understand the potential pathogenic role of each change in the GAA gene. Furthermore, a precise and early molecular analysis improves genetic counseling besides allowing for a more efficient treatment in potential candidates.