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Background Gaucher disease (GD) is a rare recessively inherited disorder caused by deficiency of a lysosomal enzyme, glucocerebrosidase. Accumulation of glucosylceramide or glucosylsphingosine in macrophages leads to increased production of ferritin and chitotriosidase and to decreases in hemoglobin concentration and platelet count, which are used as blood biomarkers. GD is treated by enzyme replacement therapy (ERT) or, sometimes by substrate reduction therapy. However, no physiological model for analysis of biomarkers change during ERT has been proposed. We aimed to develop a pathophysiological model to analyze biomarker's response to ERT and several covariates impact. Methods Changes in blood ferritin, chitotriosidase, hemoglobin and platelets were analyzed in French GD Registry patients receiving imiglucerase/alglucerase as ERT. We used simplified exponential pathophysiological model, with initial concentration, biomarkers amplitude of variation and rate constant of normalization during ERT. Changes in four biomarkers were analyzed separately and then all four together from initiation to discontinuation of ERT, or until the end of follow-up. Several covariates were tested, including age at ERT initiation, splenectomy, sex, genotype (N370S/N370S), and ERT dose. Results An exponential model gave a good data fit. The four biomarkers analysis showed that the rate of nomalization was the same for all biomarkers, with a half-life of 0.5 years. Predicted values of biomarkers at ERT's steady state were 40% and 10% of initial concentrations, for ferritin and chitotriosidase, respectively, and 120% and 200% for hemoglobin and platelets, respectively. We found that 3 covariates had an effect on initial concentration or on amplitude of variation in ferritin, hemoglobin and platelets: women and patients under 15 years of age had lower ferritin and hemoglobin concentrations, and patients under 15 years of age had higher platelet count. Splenectomized patients had higher ferritin concentrations and platelet count and lower amplitude of variation of hemoglobin. Conclusion We report the first dynamic model of biomarker changes in GD. It enabled us to estimate that 95% of biomarker response to ERT was achieved in 2 years, but with high inter-patient variability. We also found that with the current treatment, normalization of chitotriosidase and ferritin will occur in about 65% of patients. [ABSTRACT FROM AUTHOR]

Metachromatic leukodystrophy is an autosomal recessive neurodegenerative lysosomal disease characterized by a deficiency of the lysosomal enzyme arylsulfatase A and the subsequent accumulation of sulfatide in neuronal and visceral tissues. Clinical diagnosis is usually confirmed by in vitro analysis of arylsulfatase A activity butmay be complicated in cases of arylsulfatase A pseudodeficiency and sphingolipid activators protein deficiency. We report the case of a 3-year-old boy who presented a severe form of late infantile metachromatic leukodystrophy. This patient was found to be homozygous for the arylsulfatase A pseudodeficiency. This condition is rare and can lead to a severe disease. Prenatal diagnosis was performed in this family, and the fetus was healthy. [ABSTRACT FROM AUTHOR]

Fabry disease is an X-linked lysosomal deficiency of α-galactosidase A that results in cellular accumulation of galactoconjugates, mainly globotriaosylceramide, particularly in blood vessels. Neuroradiological findings include ischemic stroke, white matter lesions, vascular abnormalities (vertebrobasilar dolichoectasia and vessel tortuosity), and posterior thalamus involvement (the so called pulvinar sign). The purpose of our study was to investigate the presence of the increased pulvinar signal intensity on T1-weighted imaging – pulvinar sign and its relationship with other clinical findings, in a non-selected cohort of Fabry patients. We performed a prospective analysis of two populations of patients (36 subjects) with Fabry disease. Patients were followed-up at the Department of Internal Medicine of the Bichat Hospital in Paris (France) and at the Neurological Clinic of the University Hospital of Padova (Italy). Brain MR studies of each patient included T1- and T2- weighted images, FLAIR sequences, and in some cases diffusion weighted images. A total of 36 patients (16 males, 20 females) were investigated in 14 families. The pulvinar sign was found in 5 male patients, but not in female patients. Seven patients had had at least one stroke (territorial or lacunar). There was no correlation between stroke and the pulvinar sign. All patients with the pulvinar sign had hypertrophic cardiomyopathy. Four patients out of five with the pulvinar sign were on dialysis or had a kidney transplantation. Our findings suggest that the pulvinar sign is a highly specific sign of Fabry disease, found in male patients with cardiac signs and severe kidney involvement. [ABSTRACT FROM AUTHOR]

Background and Objectives: Intravenous imiglucerase enzyme replacement therapy for Gaucher disease type 1 administered every 2 weeks is at variance with the imiglucerase plasma half-life of a few minutes. We hypothesized that studying the pharmacokinetics of imiglucerase in blood Gaucher disease type 1 monocytes would be more relevant for understanding enzyme replacement therapy responses.Methods: Glucocerebrosidase intra-monocyte activity was studied by flow cytometry. The pharmacokinetics of imiglucerase was analyzed using a population-pharmacokinetic model from a cohort of 31 patients with Gaucher disease type 1 who either started or were receiving long-term treatment with imiglucerase.Results: A pharmacokinetic analysis of imiglucerase showed a two-compartment model with a high peak followed by a two-phase exponential decay (fast phase half-life: 0.36 days; slow phase half-life: 9.7 days) leading to a median 1.4-fold increase in glucocerebrosidase intra-monocyte activity from the pre-treatment activity (p = 0.04). In patients receiving long-term treatment, for whom the imiglucerase dose per infusion was chosen on the basis of disease aggressiveness/response, imiglucerase clearance correlated with the administered dose. However, the residual glucocerebrosidase intra-monocyte activity value was dose independent, suggesting that the maintenance of imiglucerase residual activity is patient specific. Endogenous pre-treatment glucocerebrosidase intra-monocyte activity was the most informative single parameter for distinguishing patients without (n = 10) and with a clinical indication (n = 17) for starting enzyme replacement therapy (area under the receiver operating characteristic curve: 0.912; 95% confidence interval 0.8-1; p < 0.001), as confirmed also by a factorial analysis of mixed data.Conclusion: This study provides novel pharmacokinetic data that support current imiglucerase administration regimens and suggests the existence of a glucocerebrosidase activity threshold related to Gaucher disease type 1 aggressiveness. These findings can potentially improve Gaucher disease type 1 management algorithms and clinical decision making. [ABSTRACT FROM AUTHOR]

Pompe disease is a rare disorder due to deficiency of the acid α-glucosidase (GAA) treated by enzyme replacement therapy. The present authorized treatment with rhGAA, the recombinant human enzyme, provides an important benefit in the infantile onset; however, the juvenile and adult forms of the disease corresponding to > 80% of the patients are less responsive to this treatment. This resistance has been mainly attributed to an insufficiency of mannose 6-phosphate residues in rhGAA to address lysosomes through the cation-independent mannose 6-phosphate receptor (CI-M6PR). As yet, several attempts to improve the enzyme delivery by increasing the number of mannose 6-phosphate on the enzyme were poorly effective on the late onset form of the disease. Here, we show that chemical conjugation of a synthetic analogue of the mannose 6-phosphate, named AMFA, onto rhGAA improves the affinity for CI-M6PR and the uptake of the enzyme in fibroblasts and myoblasts of adult Pompe patients. More importantly, only the conjugated rhGAA-AMFA was effective in aged Pompe mice when compared to rhGAA. Weekly treatment with 5–20 mg·kg − 1 rhGAA-AMFA provided major improvements of the motor function and of the myofiber structure, whereas rhGAA was inactive. Finally, AMFA addition did not induce supplementary immune response to the enzyme. This modified enzyme, displaying a muscle recovery in aged Pompe mice that was never attained before, could be considered as a potential therapy for the late onset Pompe disease. [ABSTRACT FROM AUTHOR]

In Infantile Onset Pompe Disease (IOPD), enzyme replacement therapy (ERT) may improve survival, cardiac function, and motor development. However, even with early enzyme replacement therapy, some patients experienced poor response to ERT and abnormal motor milestones that could be due to motor neuron involvement. In this long-term retrospective study, we analyzed concomitant clinical motor outcomes and electroneuromyography (ENMG) findings in patients with IOPD and Juvenile Onset Pompe Disease (JOPD). Twenty-nine pediatric patients were included and 20 surviving were analyzed for neuromotor studies: 12 had IOPD (group 1), 4 had JOPD (group 2) and 4 (group 3) received ERT in the first month of age. Motor nerve conduction studies were mostly normal. Needle EMG performed at diagnosis always indicated the existence of myopathy that responded to ERT. Two IOPD patients (group 1) presenting with mixed motor neuropathy and myopathy displayed a poor outcome and never walked. Two patients became non-walkers (one IOPD patient and one patient of group 3) at respectively 9 and 3 years of age. One JOPD patient is about to lose walking ability. This motor deterioration was associated with the development of a motor neuropathy. Patients older than 10 years of age develop a motor neuropathy. Initial or secondary motor neuron involvement seems to be associated with a poor motor outcome showing that ERT may fail to prevent the accumulation of glycogen in motor neuron. Neurophysiological findings are important to assess severity of motor neuron damage in all Pompe pediatric patients and should be systematically performed. [ABSTRACT FROM AUTHOR]

Background Obstructive sleep apnea syndrome (OSAS) is very common in mucopolysaccharidosis I (MPS I). Hematopoietic stem cell transplantation (HSCT) is the preferred treatment for patients with severe MPS I diagnosed early in life. The protective effect of HSCT on the development of long term OSAS is not known. Methods Overnight polysomnography (PSG) and biomarker data were analyzed during the annual follow-up in consecutive MPS I patients treated with HSCT. Results The data of 13 patients (6 boys) were analyzed. Median age at HSCT was 17 (range 14–19) months, median age at PSG was 9.0 (4.5–14.5) years, and median time elapsed since HSCT was 7.6 (2.4–13.2) years. A significant correlation was observed between time elapsed since HSCT and the apnea–hypopnea index (AHI, r 2 = 0.493, p = + 0.003) and the oxygen desaturation index (r 2 = 0.424, p = + 0.02). Patients older than 10 years of age had a higher mean AHI (25.8/h vs 1.4/h, p = 0.0008), a lower mean pulse oximetry (94.7% vs 97.2%, p = 0.01) and a higher mean hypopnea index (18.8 vs 0.71/h, p = 0.016) as compared to those younger than 10 years of age. No correlation was observed between the AHI and the metabolic clearance, assessed by urine glycosaminoglycan (GAG) excretion and residual enzyme activity, although there was a positive trend for the urinary GAG/higher normal value for age ratio (p = 0.09). Conclusion HSCT does not offer long term protection against OSAS in MPS I with OSAS being documented in all patients after a time elapse since HSCT exceeding 10 years. The potential benefit of additional enzyme replacement therapy needs to be assessed. [ABSTRACT FROM AUTHOR]

Background Recently, biallelic mutations in the Neuroblastoma Amplified Sequence NBAS gene have been identified in ten patients that present recurrent acute liver failure (RALF) in early infancy. In addition to severe liver dysfunction, some of these individuals also suffered from other comorbidities including cardiomyopathy, neurologic phenotypes and gastrointestinal immune defects. Here we report on a consanguineous Lebanese family with three siblings affected by RALF. Of note, neonatal spontaneous fractures, developmental delay, prominent eyes, generalized hirsutism, gum hypertrophy, and hepato-splenomegaly ​were also present. Methods Whole-genome SNP genotyping in all the patients, followed by exome sequencing was performed in one of the affected siblings. Results A homozygous c.409C > T (p.Arg137Trp) missense mutation in NBAS was identified in all patients. Conclusion Overall, our findings confirm the involvement of NBAS in the pathogenesis of this condition characterized by severe liver dysfunction and help expand its phenotypical spectrum. [ABSTRACT FROM AUTHOR]

Sandhoff disease (SD) is an autosomal recessive lysosomal storage disease caused by mutations in the HEXB gene encoding the beta subunit of hexosaminidases A and B, two enzymes involved in GM2 ganglioside degradation. Eleven French Sandhoff patients with infantile or juvenile forms of the disease were completely characterized using sequencing of the HEXB gene. A specific procedure was developed to facilitate the detection of the common 5′-end 16kb deletion which was frequent (36% of the alleles) in our study. Eleven other disease-causing mutations were found, among which four have previously been reported (c.850C>T, c.793T>G, c.115del and c.800_817del). Seven mutations were completely novel and were analyzed using molecular modelling. Two deletions (c.176del and c.1058_1060del), a duplication (c.1485_1487dup) and a nonsense mutation (c.552T>G) were predicted to strongly alter the enzyme spatial organization. The splice mutation c.558+5G>A affecting the intron 4 consensus splice site led to a skipping of exon 4 and to a truncated protein (p.191X). Two missense mutations were found among the patients studied. The c.448A>C mutation was probably a severe mutation as it was present in association with the known c.793T>G in an infantile form of Sandhoff disease and as it significantly modified the N-terminal domain structure of the protein. The c.171G>C mutation resulting in a p.W57C amino acid substitution in the N-terminal region is probably less drastic than the other abnormalities as it was present in a juvenile patient in association with the c.176del. Finally, this study reports a rapid detection of the Sandhoff disease-causing alleles facilitating genetic counselling and prenatal diagnosis in at-risk families. [ABSTRACT FROM AUTHOR]

Muscle glycogen storage was measured by in vivo, natural abundance 13C nuclear magnetic resonance spectroscopy in distal and proximal lower limb segments of patients suffering from adult-onset acid maltase deficiency. Interleaved T1-weighted acquisitions of glycogen and creatine served to quantify glycogen excess. For acid maltase deficient patients (n=11), glycogen:creatine was higher than controls (n=12), (1.20±0.39 vs. 0.83±0.18, P=0.0005). Glycogen storage was above the normal 95% confidence limits in at least one site for 7/11 patients. The intra-individual coefficient of reproducibility was 12%. This totally atraumatic measurement of glycogen allows repeated measurement at different muscle sites of acid maltase deficient patients, despite selective fatty replacement of tissue. This could provide an additional parameter to follow the development of disease in individual patients, including in the perspective of forthcoming therapeutic trials. It may also offer an appropriate tool to study the role of glycogen accumulation in progression of the pathology. [Copyright &y& Elsevier]

An abstract of the article "Towards Reversing Sandhoff Pathology by Lentiviral-Mediated Gene Therapy," by Audrey Arfi, Rivka Ziesling, Livia Poenaru, Anthony H. Futerman and Catherine Caillaud is presented.

Examines the genetic history of gaucher disease (GD) in Ashkenazi Jewish (AJ) N370S and 84GG acid beta-glucosidase (GBA) mutations. Use of linkage and haplotype analyses in investigating GBA mutations in AJ population; Etiology of GD; Method used to provide estimated dates for disease-causing mutations.

Neuronal ceroid lipofuscinosis type 2 (CLN2) disease is a rare, lysosomal storage disorder that causes pediatric onset neurodegenerative disease. It is characterized by mutations in the TPP1 gene. Symptoms begin between 2 and 4 years of age with loss of previously acquired motor, cognitive, and language abilities. Cerliponase alfa, a recombinant human TPP1 enzyme, is the only approved therapy. We report the first presymptomatic cerliponase alfa intraventricular treatment in a familial case of CLN2 related to a classical TPP1 variant. Sister 1 presented with motor, cognitive, and language decline and progressive myoclonic epilepsy since the age of 3 years, evolved with severe diffuse encephalopathy, received no specific treatment, and died at 11 years. Sister 2 had a CLN2 presymptomatic diagnosis and has been treated with cerliponase since she was 12 months old. She is now 6 years 8 months and has no CLN2 symptom except one generalized seizure 1 year ago. No serious adverse event has occurred. Repeated Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition standardized index scores are heterogeneous in the extremely low to low average ranges. Mean length of utterances, a global index of sentence complexity, showed a delay, but a gradual improvement. The reported case enhances the major contribution of presymptomatic diagnosis and significant middle-term treatment benefit for patients with CLN2., (© 2024 The Authors. European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology.)

Background: Classical infantile-onset Pompe disease (IOPD) is the most severe form of Pompe disease. Enzyme replacement therapy (ERT) has significantly increased survival but only a few studies have reported long-term outcomes., Methods: We retrospectively analyzed the outcomes of classical IOPD patients diagnosed in France between 2004 and 2020., Results: Sixty-four patients were identified. At diagnosis (median age 4 months) all patients had cardiomyopathy and most had severe hypotonia (57 of 62 patients, 92%). ERT was initiated in 50 (78%) patients and stopped later due to being ineffective in 10 (21%). Thirty-seven (58%) patients died during follow-up, including all untreated and discontinued ERT patients, and 13 additional patients. Mortality was higher during the first 3 years of life and after the age of 12 years. Persistence of cardiomyopathy during follow-up and/or the presence of heart failure were highly associated with an increased risk of death. In contrast, cross-reactive immunologic material (CRIM)-negative status (n = 16, 26%) was unrelated to increased mortality, presumably because immunomodulation protocols prevent the emergence of high antibody titers to ERT. Besides survival, decreased ERT efficacy appeared after the age of 6 years, with a progressive decline in motor and pulmonary functions for most survivors., Conclusions: This study reports the long-term follow-up of one of the largest cohorts of classical IOPD patients and demonstrates high long-term mortality and morbidity rates with a secondary decline in muscular and respiratory functions. This decreased efficacy seems to be multifactorial, highlighting the importance of developing new therapeutic approaches targeting various aspects of pathogenesis., (© 2023 The Authors. European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology.)

GM1 gangliosidosis is a rare lysosomal storage disorder associated with β-galactosidase enzyme deficiency. There are three types of GM1 gangliosidosis based on age of symptom onset, which correlate with disease severity. In 2019, we performed a retrospective multicentric study including all patients diagnosed with GM1 gangliosidosis in France since 1998. We had access to data for 61 of the 88 patients diagnosed between 1998 and 2019. There were 41 patients with type 1 (symptom onset ≤6 months), 11 with type 2a (symptom onset from 7 months to 2 years), 5 with type 2b (symptom onset from 2 to 3 years), and 4 with type 3 (symptom onset >3 years). The estimated incidence in France was 1/210000. In patients with type 1, the first symptoms were hypotonia (26/41, 63%), dyspnea (7/41, 17%), and nystagmus (6/41, 15%), whereas in patients with type 2a, these were psychomotor regression (9/11, 82%) and seizures (3/11, 27%). In types 2b and 3, the initial symptoms were mild, such as speech difficulties, school difficulties, and progressive psychomotor regression. Hypotonia was observed in all patients, except type 3. The mean overall survival was 23 months (95% confidence interval [CI]: 7, 39) for type 1 and 9.1 years (95% CI: 4.5, 13.5) for type 2a. To the best of our knowledge, this is one of the largest historical cohorts reported, which provides important information on the evolution of all types of GM1 gangliosidosis. These data could be used as a historical cohort in studies assessing potential therapies for this rare genetic disease., (© 2023 SSIEM.)

Mucopolysaccharidosis type I-H (MPS I-H) is a rare lysosomal storage disorder caused by α-L-Iduronidase deficiency. Early haematopoietic stem cell transplantation (HSCT) is the sole available therapeutic option to preserve neurocognitive functions. We report long-term follow-up (median 9 years, interquartile range 8-16.5) for 51 MPS I-H patients who underwent HSCT between 1986 and 2018 in France. 4 patients died from complications of HSCT and one from disease progression. Complete chimerism and normal α-L-Iduronidase activity were obtained in 84% and 71% of patients respectively. No difference of outcomes was observed between bone marrow and cord blood stem cell sources. All patients acquired independent walking and 91% and 78% acquired intelligible language or reading and writing. Intelligence Quotient evaluation (n = 23) showed that 69% had IQ ≥ 70 at last follow-up. 58% of patients had normal or remedial schooling and 62% of the 13 adults had good socio-professional insertion. Skeletal dysplasia as well as vision and hearing impairments progressed despite HSCT, with significant disability. These results provide a long-term assessment of HSCT efficacy in MPS I-H and could be useful in the evaluation of novel promising treatments such as gene therapy., (© 2022. The Author(s).)

Background: Fabry disease (FD) is an X-linked lysosomal storage disorder due to deficient alpha-galactosidase activity leading to intracellular glycosphingolipid accumulation. Multiple variants have been reported in the GLA gene coding for alpha-galactosidase, and the question of the pathogenicity of rare variants needs to be addressed, especially in patients with mild phenotypes., Case Presentation: The patient, a 37-year-old female, presented with a persistent proteinuria after an otherwise uncomplicated first pregnancy. Renal biopsy showed both mild mesangial IgA deposits, and a striking vacuolization of podocytes and tubular cells consistent with Fabry disease. On electron microscopy, discrete but characteristic pseudo-myelinic lamellar inclusions were observed in the podocytes' lysosomes. A more detailed physical examination revealed an angiokeratoma, and medical history ancient acroparesthesia. There was no cardiac or cerebral involvement of Fabry disease on magnetic resonance imaging. While blood enzymatic activity of alpha-ga lactosidase was normal in this patient, lysoGb3 was elevated (3 N), and a rare heterozygous variant called c.610 T > C was documented in GLA gene. The patient was treated with an ACE inhibitor, with a rapid decrease in proteinuria. After a 5-year follow-up, her renal function has remained normal, with mild proteinuria, and normal cardiac echography., Conclusions: We report and phenotypically describe the first case of a Fabry disease female patient carrying the GLA c.610 T > C variant associated with a renal-predominant clinical presentation.

Pompe disease (PD) is caused by a deficiency of lysosomal acid α-glucosidase resulting from mutations in the GAA gene. The clinical spectrum ranges from a rapidly fatal multisystemic disorder (classic PD, onset < 1 year) to a milder adult onset myopathy. The aims of this study were to characterize the GAA mutations, to establish the disease epidemiology, and to identify potential genotype-phenotype correlations in French late-onset PD patients (onset ≥ 2 years) diagnosed since the 1970s. Data were collected from the two main laboratories involved in PD diagnosis and from the French Pompe registry. Two hundred forty-six patients (130 females and 116 males) were included, with a mean age at diagnosis of 43 years. Eighty-three different mutations were identified in the GAA gene, among which 28 were novel. These variants were spread all over the sequence and included 42 missense (one affecting start codon), 8 nonsense, 15 frameshift, 14 splice mutations, 3 small in-frame deletions, and one large deletion. The common c.-32-13T>G mutation was detected in 151/170 index cases. Other frequent mutations included the exon 18 deletion, the c.525del, and the missense mutations c.1927G>A (p.Gly643Arg) and c.655G>A (p.Gly219Arg). Patients carrying the c.-32-13T>G mutation had an older mean age at onset than patients non-exhibiting this mutation (36 versus 25 years). Patients with the same genotype had a highly variable age at onset. We estimated the frequency of late-onset PD in France around 1/69,927 newborns. In conclusion, we characterized the French cohort of late-onset PD patients through a nationwide study covering more than 40 years.

Neuronal ceroid lipofuscinoses (NCL) represent a group of autosomal recessive neurodegenerative disorders, presenting with myoclonic epilepsy, psychomotor delay, progressive loss of vision, and early death. Four main clinical forms have been delineated (infantile, late infantile, juvenile, and adult), but many other variants have also been described. At least 14 genetically distinct NCL, designated CLN1 to CLN14, are presently known.The identification of the deficient protein and/or the genetic defect is required for a specific diagnosis, which is necessary for a reliable genetic counseling in at-risk families., (Copyright © 2013 Elsevier B.V. All rights reserved.)

RNA interference has emerged as a powerful technique to down-regulate gene expression. The lentiviral vector-mediated expression of small hairpin RNAs (shRNAs) from polymerase III promoters allows permanent down-regulation of a specific gene in a wide range of cell types both in vitro and in vivo. In this chapter, we describe a method permitting the expression of shRNA from lentiviral vectors in primary murine myogenic cells. We designed shRNAs targeted to the muscular glycogen synthase isoform (shGYS1), a highly regulated enzyme responsible for glycogen synthesis, in order to modulate the muscle glycogen biosynthetic pathway and to improve the phenotype in primary myogenic cells from a murine model of glycogen storage disease type II (GSDII). This method based on shRNA-mediated down-regulation could be applied to other muscular disorders to evaluate new therapeutic options.

Background: Gaucher disease (GD) is a sphingolipidosis with heterogeneous phenotypic expression. The vital and / or functional prognosis may be threatened by an early visceral severe involvement in type 1 or a neurological degeneration in the more rarest neuroneupathic forms. The phenotypic and genotypic data regarding Gaucher disease are poorly known in Maghrebian countries; they are even less for pediatric forms. THE AIM of the study is to highlight the specific phenotypic and genotypic changing among the widest Gaucher pediatric cohort in the Tunisian population., Methods: a restrospective study of a sample oh children in voluved by gaucher disease., Results: Twenty one cases of GD were identified, divided into 13 cases with type 1, 5 with type 3 and 3 children with acute neurological form. The first symptoms occurred before 1 year age in one third of patients with type IGD. The clinical phenotype was severe according to the high severity score index and proportion of growth retardation. Portal hypertension was found in 8 patients. Three type 3 GD patients died before occurrence of the neurological signs. The phenotype was intermediate between the classic type 2 GD and its perinatal lethal variant. Three patients were treated with enzyme replacement therapy and 4 others had allogenic bone marrow transplantation with a favorable outcome. Three mutations dominate the genotypic spectrum of GD in this cohort. Additionally to the N370 mutation, L444P and RecNciI mutations seem to occur more frequently compared to the GD forms presenting in adulthood., Conclusion: This data confirm the particular severity of Gaucher disease manifesting in childhood. This was enhanced through the high frequency of severe mutations. Further studies on largest cohort are needed to more clarify the phenotypic and genotypic features of Gaucher disease in Tunisia.

Glycogen storage disease type II (GSDII) is an autosomal recessive disorder caused by defects in the acid alpha-glucosidase (GAA) gene leading to lysosomal glycogen accumulation, mainly in cardiac and muscle tissues. In order to facilitate biological investigation on this disease and to avoid time-consuming direct cell isolation and culture, we have established murine myogenic GSDII cell lines. Lentiviral/retroviral expression of SV40 T antigen, Bmi-1 or cyclin-dependent kinase 4 (CDK4) genes was used to induce the immortalization of primary satellite cells from GSDII mice. The resulting immortalized myoblasts exhibit phenotypic characteristics of their parental cells, including profound GAA deficiency, glycogen accumulation and the ability to fully differentiate into myotubes when placed in proper culture conditions. These cell lines will constitute a powerful tool for both basic and applied studies focused on a better understanding of the pathophysiological mechanisms involved in GSDII and for assessing putative therapeutic strategies.

Alterations in GLB1, the gene coding for acid beta-D-galactosidase (beta-Gal), can result in GM1 gangliosidosis (GM1), a neurodegenerative disorder, or in Morquio B disease (MBD), a phenotype with dysostosis multiplex and normal central nervous system (CNS) function. While most MBD patients carry a common allele, c.817TG>CT (p.W273L), only few of the >100 mutations known in GM1 can be related to a certain phenotype. In 25 multiethnic patients with GM1 or MBD, 11 missense mutations were found as well as one novel insertion and a transversion causing aberrant gene products. Except c.602G>A (p.R201H) and two novel alleles, c.592G>T (p.D198Y) and c.1189C>G (p.P397A), all mutants resulted in significantly reduced beta-Gal activities (<10% of normal) upon expression in COS-1 cells. Although c.997T>C (p.Y333H) expressed 3% of normal activity, the mutant protein was localized in the lysosomal-endosomal compartment. A homozygous case presented with late infantile GM1, while a heterozygous, juvenile case carried p.Y333H together with p.R201H. This allele, recently found in homozygous MBD, gives rise to rough endoplasmic reticulum (RER)-located beta-Gal precursors. Thus, unlike classical MBD, the phenotype of heterozygotes carrying p.R201H may rather be determined by poorly active, properly transported products of the counter allele than by the mislocalized p.R201H precursors.

Aim: We report through the first Tunisian experience with enzyme replacement therapy, the goals and consensus recommendations for treatment and monitoring of paediatric non neuronopathic Gaucher disease., Methods: Three children with Gaucher disease undergone enzyme replacement therapy with Cerezyme for severe visceral and/or bone involvement. Visceral, hematologic, bone, and growth parameters were assessed initially and under treatment., Results: Two children presented with severe visceral or hematologic picture. One patient had myocardiopathy and primitive portal hypertension and another was diagnosed with cirrhosis related to Gaucher disease. Recurrent avascular necrosis and osteoporosis have justified treatment in another child. All patients received an initial dose of 60U/Kg/2 weeks. We have seen a gradual disappearance of hepatosplenomegaly and a rapid normalisation of hematological parameters in two patients. A resistance to treatment indicated splenectomy in one patient. The improvement in bone mineral density was slower. A significant growth gain was observed in patients with growth retardation. No patient had developed Cerezyme antibodies., Conclusion: Despite its effectiveness and safety demonstrated in these children, enzyme replacement therapy remains inaccessible because of its cost for emerging countries. The allogeneic bone marrow is an alternative therapy to encourage and to propose precociously for severe paediatric forms of Gaucher disease.

Background: Glycogen storage disease type II (GSDII) or Pompe disease is an inherited disease of glycogen metabolism caused by a lack of functional lysosomal acid alpha-glucosidase (GAA). Affected individuals store glycogen in lysosomes resulting in fatal hypertrophic cardiomyopathy and respiratory failure in the most severe form. Even if enzyme replacement therapy (ERT) has already proven some efficacy, its results remain heterogeneous in skeletal muscle, especially in cross reactive immunological material (CRIM)-negative patients. We investigated for the first time the use of hematopoietic stem cell (HSC) gene therapy in a murine model of GSDII., Methods: Deficient HSC were transduced with a lentiviral vector expressing human GAA or enhanced green fluorescent protein (GFP) under the control of the retroviral MND promoter and transplanted into lethally irradiated GSDII mice. Animals were then subjected to an ERT protocol for 5 weeks and monitored for metabolic correction and GAA-induced immune reaction., Results: GAA was expressed as a correctly processed protein, allowing a complete enzymatic correction in transduced deficient cells without toxicity. Seventeen weeks after transplantation, a partial restoration of the GAA enzymatic activity was observed in bone marrow and peripheral blood cells of GSDII mice, allowing a significant glycogen clearance in skeletal muscle. ERT induced a robust antibody response in GFP-transplanted mice, whereas no immune reaction could be detected in GAA-transplanted mice., Conclusions: Lentiviral vector-mediated HSC gene therapy leads to a partial metabolic correction and induces a tolerance to ERT in GSDII mice. This strategy could enhance the efficacy of ERT in CRIM-negative Pompe patients.

Background: beta-Mannosidosis is a rare inborn error of metabolism with various phenotypes, including mental retardation, behavioral problems, hearing loss, and recurrent airway infections in childhood. To our knowledge, there is no published description of Gilles de la Tourette syndrome in association with this enzymatic deficiency., Objective: To describe a unique case of Gilles de la Tourette syndrome associated with beta-mannosidosis., Setting: University hospital. Patient An 18-year-old man exhibited motor and vocal tics since childhood, attention-deficit/hyperactivity disorder, impulsivity, and aggressiveness compatible with Gilles de la Tourette syndrome. A screen for inborn errors of metabolism was made because of the atypical association with slight mental retardation and bilateral perceptive hypoacousia., Results: Urinary analysis showed disacchariduria, and leukocyte analysis revealed a profound deficit in beta-mannosidase activity. Two novel mutations in the beta-mannosidase gene were found: a new splice mutation in one allele, and a unique 10-base-pair insertion in the other., Conclusions: This case illustrates the phenotypic variability of inborn errors of metabolism in adults and demonstrates the need to screen inborn errors of metabolism in atypical Gilles de la Tourette syndrome.

We report a case of GM2 gangliosidosis revealed by MR imaging of an isolated brain stem abnormality in a 3-year-old girl referred for gait difficulties related to ataxia and pyramidal signs. Brain MR imaging displayed a brain stem lesion with high signal intensity on fluid-attenuated inversion recovery and T2-weighted images, suggesting either a tumor or an inflammatory process. Stereotactic biopsy findings showed the presence of swollen neurons with storage material in lysosomes. Enzyme study revealed deficiency of hexosaminidase A, variant B1. Gangliosidoses should be considered in the differential diagnosis of isolated infiltrating brain stem lesions in childhood.

Gaucher and Fabry's diseases are lysosomal storage disorders. They are due to glucocerebrosidase or alpha galactosidase deficiency, respectively. Gaucher disease, transmitted as an autosomal recessive trait, is frequent among Ashkenazi Jews. Cloning of the gene has allowed the characterization of few common mutations. Some of them have a prognosis value, in favour of either a non neurological form (type 1) or more severe forms (types 2 and 3). There mutations were found in 70% of the alleles, the other alleles carrying private mutations. Fabry disease is transmitted as an X-linked recessive trait. Genetic counselling in at-risk families relies on the detection of carrier females. As the alpha galactosidase gene shows various mutations, the establishment of phenotype-genotype correlations is limited. These two diseases, well defined at the biochemical and genetic level, are good models of inherited diseases for the development of specific therapies.