Early Visual Seizures and Progressive Myoclonus Epilepsy in Neuronopathic Gaucher Disease Due to a Rare Compound Heterozygosity (N188S/S107L)

Long-term efficacy of low-dose perampanel for progressive myoclonus epilepsy in a patient with Gaucher disease type 3

PURPOSE

We report the case of a patient with progressive myoclonus epilepsy due to Gaucher disease type 3 whose seizures and ability to perform activities of daily living were significantly improved after starting low-dose perampanel therapy.

CASE

Our patient's generalized tonic-clonic seizures and myoclonus did not improve despite the administration of multiple antiseizure medications and enzyme replacement therapy. The myoclonus reduced following pharmacological chaperone therapy, but this effect was temporary, and the generalized tonic-clonic seizures continued to occur. However, the generalized tonic-clonic seizures disappeared following treatment with 2 mg/day of perampanel. In addition, the decrease in myoclonus dramatically improved motor function such as talking, eating, and walking and stabilized the patient's mental status. These effects have been sustained for more than 4 years.

CONCLUSION

Perampanel is expected to be effective in the treatment of progressive myoclonus epilepsy associated with Gaucher disease type 3 and should be considered the drug of choice for this condition.

Diagnosing neuronopathic Gaucher disease: New considerations and challenges in assigning Gaucher phenotypes

Gaucher disease (GD), resulting from biallelic mutations in the gene GBA1, is a monogenic recessively inherited Mendelian disorder with a wide range of phenotypic presentations. The more severe forms of the disease, acute neuronopathic GD (GD2) and chronic neuronopathic GD (GD3), also have a continuum of disease severity with an overlap in manifestations and limited genotype-phenotype correlation. In very young patients, assigning a definitive diagnosis can sometimes be challenging. Several recent studies highlight specific features of neuronopathic GD that may provide diagnostic clues. Distinguishing between the different GD types has important therapeutic implications. Currently there are limited treatment options specifically for neuronopathic GD due to the difficulty in delivering therapies across the blood-brain barrier. In this work, we present both classic and newly appreciated aspects of the Gaucher phenotype that can aid in discriminating between acute and chronic neuronopathic GD, and highlight the continuing therapeutic challenges.

In vitro and in vivo effects of Ambroxol chaperone therapy in two Italian patients affected by neuronopathic Gaucher disease and epilepsy

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder caused by mutations in the acid β-glucosidase encoding gene (GBA1), resulting in the deficient activity of acid β-glucosidase (GCase). To date, there is no approved treatment for the neurological manifestations of the disease. The role of Ambroxol as a chaperone for mutant GCase has been extensively demonstrated in vitro. Furthermore, different authors have reported beneficial effects of high doses of Ambroxol on neurological manifestations in patients affected by GD.

In this report, we describe the in vitro and in vivo effects of Ambroxol in two patients (P1 and P2) affected by the neurological form of GD and epilepsy, carrying mutations already reported as responsive to the chaperone. Indeed, P1 presented the N188S mutation in compound heterozygous with a null allele (IVS2 + 1G > A) and P2 was homozygous for the L444P mutation. As expected, a beneficial effect of Ambroxol was observed in cultured fibroblasts as well as in vivo, both on epilepsy and on biomarkers of GD, in P1. However, Ambroxol was completely undefective in P2, suggesting that other factors besides the GBA1 mutation itself would be involved in the response therapy which would be difficult to predict based on the patient genotype. The present report expands the experience of Ambroxol treatment in neurological GD patients and highlights the need to in vitro test the individual response to Ambroxol even in patients carrying mutations already classified as responsive to the chaperone.

High-frequency component in flash visual evoked potentials in type 3 Gaucher disease

OBJECTIVE

To characterize the visual evoked potentials (VEP) in patients with type 3 Gaucher disease (GD) with or without progressive myoclonus epilepsy.

METHODS

Three young adults with progressive myoclonus epilepsy (type 3a GD) and two children without progressive myoclonus epilepsy (type 3b GD) were enrolled. Flash visual and somatosensory evoked potentials (F-VEP and SEP, respectively) were retrospectively reviewed in all patients under enzyme replacement therapy. Pattern reversal visual evoked potentials (PR-VEP) were recorded in the type 3a group.

RESULT

High-frequency components were provoked at early latencies on averaged F-VEP in all patients with type 3a and one patient with type 3b GD. Conversely, no activities were recorded in PR-VEP. The onset latency of the components began at 15.3-19.8 ms after flash stimulation. Four-five of the F-VEP examination the activities' duration overrode the N75 waveforms and were prolonged toward the P100 peak latency. The F-VEP amplitude did not differ between the type 3a and type 3b groups, while the SEP amplitude was higher in the type 3a than in the type 3b group.

SIGNIFICANCE

High-frequency components on F-VEP using bandpass filter at 10-200 Hz may help assess augmented excitability in the visual cortex of type 3 GD patients.

First Clinicogenetic Description of Parkinson's Disease Related to GBA Mutation S107L

Background

Mutations in the glucocerebrosidase gene (GBA) are a common genetic risk factor for Parkinson's disease (PD). Mutations in the N-terminus part of GBA are less commonly found in association with PD than those in the C-terminus. Phenotypic characterization of GBA-related PD has been challenging, in part attributed to differential impact of distinct GBA mutations.

Aim

To provide a phenotypic description of two patients with PD heterozygous for the GBA mutation S107L. The S107L mutation is located in the catalytic domain of glucocerebrosidase and has not previously been reported in patients with PD.

Methods

Motor and nonmotor symptoms (NMS) of PD were evaluated using established rating scales and questionnaires. The genotype was determined by Sanger sequencing.

Results

Two half-brothers, both heterozygous carriers of S107L, exhibited an early PD onset with several NMS.

Conclusions

In these patients, heterozygosity for S107L was associated with an early onset of PD with NMS.

Progressive myoclonus epilepsy in Gaucher Disease due to a new Gly-Gly mutation causing loss of an Exonic Splicing Enhancer

BACKGROUND

Patients with Gaucher Disease (GD) exhibit three phenotypes, including type 1 (non-neuronopathic), type 2 (acute neuronopathic), and type 3 (subacute neuronopathic).

AIM

Identifying which GBA changes represent benign polymorphisms and which may result in disease-causing mutations is essential for diagnosis and genotype/phenotype correlations but is often challenging.

RESULTS

Here, we describe a patient with type 3 GD, presenting with drug-resistant epilepsy, who bears a set of GBA polymorphic variants including the novel c.363A > G (Gly82Gly) synonymous mutation. In silico predictions, mRNA and functional studies revealed that the new Gly82Gly mutation causes skipping of GBA exon 4, leading to a severe reduction of the wild type GBA mRNA. This is the first report of a synonymous change causing GD through loss of an exonic splicing enhancer sequence. The synonymous mutation is in trans with the Asn188Ser missense mutation, thus making the Asn188Ser responsible for the patient's phenotype and strengthening the association of Asn188Ser with the particular neurological phenotype of type 3 GD.

CONCLUSION

We strengthen the association of Asn188Ser with the type 3 GD phenotype and progressive myoclonus epilepsy. Our data confirm that in silico predictions and mRNA analysis are mandatory in discriminating pathological mutations from the background of harmless polymorphisms, especially synonymous changes.

Long term effects of enzyme replacement therapy in an Italian cohort of type 3 Gaucher patients

BACKGROUND

The chronic neuropathic form of Gaucher disease (GD3) is characterised by hepatosplenomegaly, anaemia, thrombocytopenia, bone alterations and central neurological involvement. Enzyme replacement therapy (ERT) has been demonstrated to be effective in non neuropathic Gaucher disease, but long term results in patients with GD3 are still limited and contrasting. A possible role of genotype in determining the response to ERT has been hypothesised.

PATIENTS AND METHODS

All patients affected by GD3, treated with ERT, and followed-up in 4 different Italian centres (Udine, Catanzaro, Sassari and Florence) were included. Data on clinical conditions, laboratory values, neurological and neuropsychological examinations, radiological and electrophysiological features were collected retrospectively from clinical records.

RESULTS

Ten patients (6 females, 4 males) with four different genotypes (L444P/L444P, L444P/F231I, P159T/unknown, C.115+1G>A/N188S) were identified. They received ERT infusions from 3 to 21years. Haematological parameters and organomegaly improved/normalised in all patients. Three patients showed severe progressive skeletal deformities. 6/10 patients were neurologically asymptomatic when they started ERT for systemic symptoms. During the follow-up, 2/6 developed an important central nervous system disease; 2/6 developed mild central symptoms; and 2/6 did not show any neurological symptom after 5, and 20years of treatment respectively, despite the presence of epileptiform abnormalities at the electroencephalogram. Overall, neurological involvement worsened over time in 6/10 patients, 3 of whom developed progressive myoclonic encephalopathy and died.

CONCLUSIONS

ERT improved the systemic manifestations in patients with GD3, but was not able to counteract the progression of neurological symptoms in the long term.

Functional analysis of 11 novel GBA alleles

Gaucher disease is the most frequent lysosomal storage disorder due to the deficiency of the acid β-glucosidase, encoded by the GBA gene. In this study, we report the structural and functional characterization of 11 novel GBA alleles. Seven single missense alleles, P159S, N188I, E235K, P245T, W312S, S366R and W381C, and two alleles carrying in cis mutations, (N188S; G265R) and (E326K; D380N), were studied for enzyme activity in transiently transfected cells. All mutants were inactive except the P159S, which retained 15% of wild-type activity. To further characterize the alleles carrying two in cis mutations, we expressed constructs bearing singly each mutation. The presence of G265R or D380N mutations completely abolished enzyme activity, while N188S and E326K mutants retained 25 and 54% of wild-type activity, respectively. Two mutations, affecting the acceptor splice site of introns 5 (c.589-1G>A) and 9 (c.1389-1G>A), led to the synthesis of aberrant mRNA. Unpredictably, family studies showed that two alleles resulted from germline or 'de novo' mutations. These results strengthen the importance of performing a complete and accurate molecular analysis of the GBA gene in order to avoid misleading conclusions and provide a comprehensive functional analysis of new GBA mutations.

Progressive myoclonus epilepsy

The progressive myoclonus epilepsies (PMEs) consist of a group of diseases with myoclonic seizures and progressive neurodegeneration, with onset in childhood and/or adolescence. Lafora disease is a neuronal glycogenosis in which normal glycogen is transformed into starch-like polyglucosans that accumulate in the neuronal somatodendritic compartment. It is caused by defects of two genes of yet unknown function, one encoding a glycogen phosphatase (laforin) and the other an ubiquitin E3 ligase (malin). Early cognitive deterioration, visual seizures affecting over half, and slowing down of EEG basic activity are three major diagnostic clues. Unverricht-Lundborg disease is presently thought to be due to damage to neurons by lysosomal cathepsins and reactive oxygen species due to absence of cystatin B, a small protein that inactivates cathepsins and, by ways yet unknown, quenches damaging redox compounds. Preserved cognition and background EEG activity, action myoclonus early morning and vertex spikes in REM sleep are the diagnostic clues. Sialidosis, with cherry-red spot, neuronopathic Gaucher disease, with paralysis of verticality, and ataxia-PME, with ataxia at onset in the middle of the first decade, are also lysosomal diseases. How the lysosomal defect culminates in myoclonus and epilepsy in these conditions remains unknown.

Cell surface associated glycohydrolases in normal and Gaucher disease fibroblasts

Gaucher disease (GD) is the most common lysosomal disorder and is caused by an inherited autosomal recessive deficiency in β-glucocerebrosidase. This enzyme, like other glycohydrolases involved in glycosphingolipid (GSL) metabolism, is present in both plasma membrane (PM) and intracellular fractions. We analyzed the activities of CBE-sensitive β-glucosidase (GBA1) and AMP-DNM-sensitive β-glucosidase (GBA2) in total cell lysates and PM of human fibroblast cell lines from control (normal) subjects and from patients with GD clinical types 1, 2, and 3. GBA1 activities in both total lysate and PM of GD fibroblasts were low, and their relative percentages were similar to those of control cells. In contrast, GBA2 activities were higher in GD cells than in control cells, and the degree of increase differed among the three GD types. The increase of GBA2 enzyme activity was correlated with increased expression of GBA2 protein as evaluated by QRT-PCR. Activities of β-galactosidase and β-hexosaminidase in PM were significantly higher for GD cells than for control cells and also showed significant differences among the three GD types, suggesting the occurrence of cross-talk among the enzymes involved in GSL metabolism. Our findings indicate that the profiles of glycohydrolase activities in PM may provide a valuable tool to refine the classification of GD into distinct clinical types.

Sequence and copy number analyses of HEXB gene in patients affected by Sandhoff disease: functional characterization of 9 novel sequence variants

Sandhoff disease (SD) is a lysosomal disorder caused by mutations in the HEXB gene. To date, 43 mutations of HEXB have been described, including 3 large deletions. Here, we have characterized 14 unrelated SD patients and developed a Multiplex Ligation-dependent Probe Amplification (MLPA) assay to investigate the presence of large HEXB deletions. Overall, we identified 16 alleles, 9 of which were novel, including 4 sequence variation leading to aminoacid changes [c.626C>T (p.T209I), c.634C>A (p.H212N), c.926G>T (p.C309F), c.1451G>A (p.G484E)] 3 intronic mutations (c.1082+5G>A, c.1242+1G>A, c.1169+5G>A), 1 nonsense mutation c.146C>A (p.S49X) and 1 small in-frame deletion c.1260_1265delAGTTGA (p.V421_E422del). Using the new MLPA assay, 2 previously described deletions were identified. In vitro expression studies showed that proteins bearing aminoacid changes p.T209I and p.G484E presented a very low or absent activity, while proteins bearing the p.H212N and p.C309F changes retained a significant residual activity. The detrimental effect of the 3 novel intronic mutations on the HEXB mRNA processing was demonstrated using a minigene assay. Unprecedentedly, minigene studies revealed the presence of a novel alternative spliced HEXB mRNA variant also present in normal cells. In conclusion, we provided new insights into the molecular basis of SD and validated an MLPA assay for detecting large HEXB deletions.

A French experience of type 3 Gaucher disease: Phenotypic diversity and neurological outcome of 10 patients

OBJECTIVE

To describe the clinical presentation of 10 patients with type 3 Gaucher disease and the clinical evolution of nine of them following specific therapy regimes.

METHODS

The follow-up of these 10 patients was between 2 and 15 years. The clinical history was provided by each patient's general practitioner and a final clinical evaluation was made by two different physicians including a neurologist. One patient received no treatment, eight received enzyme replacement therapy (ERT) and one received ERT combined with substrate reduction therapy (SRT, miglustat).

RESULTS

The clinical presentations were heterogeneous and most phenotypes reported for type 3 Gaucher disease were represented. The neurological involvement stabilized or improved in six patients under ERT with a follow-up of 2-15 years. Four of them showed isolated oculomotor signs only that improved or remained unchanged during the follow-up. Of two patients with progressive myoclonic epilepsy, the outcome was clearly unfavorable in one receiving ERT and disputable for the other receiving ERT+SRT. An unfavorable neurological outcome was observed in another patient in whom the ERT dose had been reduced before clinical decline.

CONCLUSION

The stabilization of the clinical course in most patients is noteworthy. Though further evidence is needed from a larger series in order to draw any definite conclusions, our data suggest that ERT may be effective in preventing the evolution of neurological disturbances associated with type 3 Gaucher disease in some patients. However, the clinical course of the two patients with progressive myoclonic epilepsy was not influenced by ERT, as previously reported. In accordance with that reported in the literature, data from our series suggest that the outcome of patients undergoing ERT depends on the type of clinical involvement, treatment onset and dose. Genotype may also be an important factor, with p.L444P/p.L444P possibly indicating a better outcome.

Gaucher disease patient with myoclonus epilepsy and a novel mutation

The N188S mutation in Gaucher disease is associated with myoclonus epilepsy. We performed genetic analysis on a patient with progressive myoclonus epilepsy, who had received antiepileptic drugs for over 10 years. We detected N188S/G199D on the gene encoding glucocerebrosidase. Mutant proteins carrying each mutation were expressed in COS-1 cells (a commonly used cell line which derives from kidney cells of the African green monkey). Measurements of enzymatic activity and Western blotting analysis were performed. When residual activities were measured, glucocerebrosidase with the N188S mutation exhibited 50% activity of the wild type, and with G199D, 7.4%. Neither mutation influenced the stability of the enzyme protein. These data suggested a diagnosis of Gaucher disease for this patient, and indicated that G199D is a novel mutation.

Genetic and clinical features of patients with Gaucher disease in Hungary

The aim of this study was to identify mutations in the gene encoding for lysosomal beta-glucocerebrosidase (GBA; gene symbol, GBA) in Hungarian patients with Gaucher disease (GD), and to study genotype-phenotype relationships. Genotypes and allele variations in 27 patients with type I GD of 25 unrelated families were studied. Of the 54 mutant alleles, we detected 38 frequent (N370S, 22/54; RecNciI, 8/54; L444P, 8/54) and 9 rare (N188S, R257Q, R285C, G377S, R120W, T323I, 84GG, 1263-1317del and 1263-1317del/RecTL) mutations. In addition, we identified two novel mutations. The N370S/RecNciI genotype found in 8 patients and the N370S/L444P genotype found in 5 patients were the most frequent genotypes in this cohort. In 22 patients the mutations occurred in heterozygosity with the N370S sequence variant, and one patient was homozygous for the L444P mutation. These data suggest that N370S, RecNciI, and L444P are the most prevalent mutations in Hungarian patients with GD. This mutation profile is characteristic for a Caucasian (non-Jewish) population. The c.260G>A and c.999G>A missense mutations are described here for the first time in GD patients contributing to the panel of reported GBA mutations.

Gaucher mutation N188S is associated with myoclonic epilepsy

The recent article by Montfort et al. [2004] reported a functional analysis of 13 glucocerebrosidase alleles, including mutation N188S, which they considered to be a "very mild mutation" or "modifier variant." Our clinical experience with patients carrying this mutation and preliminary protein modeling data lead us to dispute this conclusion.