Clinical spectrum of BICD2 mutations.

BACKGROUND AND PURPOSE: Mutations in the BICD2 gene cause autosomal dominant lower extremity-predominant spinal muscular atrophy 2A (SMALED2A), a condition that is associated with a specific pattern of thigh and calf muscle involvement when studied by magnetic resonance imaging (MRI). Patients may present minor clinical sensory impairment, but objective sensory involvement has yet to be demonstrated. METHODS: We collected clinical data from 11 patients from five different families carrying mutations in BICD2. Genetic diagnosis was achieved using gene panel testing and skin biopsies were taken from two patients to study the epidermal nerve fiber density. RESULTS: In the studied patients, three new pathogenic mutations were detected as well as the already defined pathogenic p.Ser107Leu mutation. The most frequent clinical picture was characterized by lower-limb weakness in combination with foot deformities. One patient manifested clinical and electrophysiological sensory impairment, and the epidermal nerve fiber density study of another patient revealed the existence of a small-fiber neuropathy. Muscle MRI showed a common pattern of fat deposition including selective involvement of gluteus medius and minimus at the pelvic level, the anterior compartment of the thigh and the posterior compartment of the calf, with only mild or no involvement of the intrinsic foot muscles. CONCLUSIONS: We report three new pathogenic mutations in the BICD2 gene. Muscle MRI confirms the existence of a selective pattern of thigh and leg muscle involvement in SMALED2A, providing additional information regarding pelvic and foot muscles. Moreover, our results raise the possibility of sensory involvement in the disease.

POGLUT1 biallelic mutations cause myopathy with reduced satellite cells, α-dystroglycan hypoglycosylation and a distinctive radiological pattern.

Protein O-glucosyltransferase 1 (POGLUT1) activity is critical for the Notch signaling pathway, being one of the main enzymes responsible for the glycosylation of the extracellular domain of Notch receptors. A biallelic mutation in the POGLUT1 gene has been reported in one family as the cause of an adult-onset limb-girdle muscular dystrophy (LGMD R21; OMIM# 617232). As the result of a collaborative international effort, we have identified the first cohort of 15 patients with LGMD R21, from nine unrelated families coming from different countries, providing a reliable phenotype-genotype and mechanistic insight. Patients carrying novel mutations in POGLUT1 all displayed a clinical picture of limb-girdle muscle weakness. However, the age at onset was broadened from adult to congenital and infantile onset. Moreover, we now report that the unique muscle imaging pattern of "inside-to-outside" fatty degeneration observed in the original cases is indeed a defining feature of POGLUT1 muscular dystrophy. Experiments on muscle biopsies from patients revealed a remarkable and consistent decrease in the level of the NOTCH1 intracellular domain, reduction of the pool of satellite cells (SC), and evidence of α-dystroglycan hypoglycosylation. In vitro biochemical and cell-based assays suggested a pathogenic role of the novel POGLUT1 mutations, leading to reduced enzymatic activity and/or protein stability. The association between the POGLUT1 variants and the muscular phenotype was established by in vivo experiments analyzing the indirect flight muscle development in transgenic Drosophila, showing that the human POGLUT1 mutations reduced its myogenic activity. In line with the well-known role of the Notch pathway in the homeostasis of SC and muscle regeneration, SC-derived myoblasts from patients' muscle samples showed decreased proliferation and facilitated differentiation. Together, these observations suggest that alterations in SC biology caused by reduced Notch1 signaling result in muscular dystrophy in LGMD R21 patients, likely with additional contribution from α-dystroglycan hypoglycosylation. This study settles the muscular clinical phenotype linked to POGLUT1 mutations and establishes the pathogenic mechanism underlying this muscle disorder. The description of a specific imaging pattern of fatty degeneration and muscle pathology with a decrease of α-dystroglycan glycosylation provides excellent tools which will help diagnose and follow up LGMD R21 patients.

Molecular characterization of congenital myasthenic syndromes in Spain.

Congenital myasthenic syndromes (CMS) are a heterogeneous group of genetic disorders, all of which impair neuromuscular transmission. Epidemiological data and frequencies of gene mutations are scarce in the literature. Here we describe the molecular genetic and clinical findings of sixty-four genetically confirmed CMS patients from Spain. Thirty-six mutations in the CHRNE, RAPSN, COLQ, GFPT1, DOK7, CHRNG, GMPPB, CHAT, CHRNA1, and CHRNB1 genes were identified in our patients, with five of them not reported so far. These data provide an overview on the relative frequencies of the different CMS subtypes in a large Spanish population. CHRNE mutations are the most common cause of CMS in Spain, accounting for 27% of the total. The second most common are RAPSN mutations. We found a higher rate of GFPT1 mutations in comparison with other populations. Remarkably, several founder mutations made a large contribution to CMS in Spain: RAPSN c.264C > A (p.Asn88Lys), CHRNE c.130insG (Glu44Glyfs*3), CHRNE c.1353insG (p.Asn542Gluf*4), DOK7 c.1124_1127dup (p.Ala378Serfs*30), and particularly frequent in Spain in comparison with other populations, COLQ c.1289A > C (p.Tyr430Ser). Furthermore, we describe phenotypes and distinguishing clinical signs associated with the various CMS genes which might help to identify specific CMS subtypes to guide diagnosis and management.

Circulating miR-323-3p is a biomarker for cardiomyopathy and an indicator of phenotypic variability in Friedreich's ataxia patients.

MicroRNAs (miRNAs) are noncoding RNAs that contribute to gene expression modulation by regulating important cellular pathways. In this study, we used small RNA sequencing to identify a series of circulating miRNAs in blood samples taken from Friedreich's ataxia patients. We were thus able to develop a miRNA biomarker signature to differentiate Friedreich's ataxia (FRDA) patients from healthy people. Most research on FDRA has focused on understanding the role of frataxin in the mitochondria, and a whole molecular view of pathological pathways underlying FRDA therefore remains to be elucidated. We found seven differentially expressed miRNAs, and we propose that these miRNAs represent key mechanisms in the modulation of several signalling pathways that regulate the physiopathology of FRDA. If this is the case, miRNAs can be used to characterize phenotypic variation in FRDA and stratify patients' risk of cardiomyopathy. In this study, we identify miR-323-3p as a candidate marker for phenotypic differentiation in FRDA patients suffering from cardiomyopathy. We propose the use of dynamic miRNAs as biomarkers for phenotypic characterization and prognosis of FRDA.

Phenotypic heterogeneity in two large Roma families with a congenital myasthenic syndrome due to CHRNE 1267delG mutation. A long-term follow-up.

Congenital myasthenic syndromes (CMS) are a heterogeneous group of genetic disorders. Mutations in CHRNE are one of the most common cause of them and the ɛ1267delG frameshifting mutation is described to be present on at least one allele of 60% of patients with CHRNE mutations. We present a comprehensive description of the heterogeneous clinical features of the CMS caused by the homozygous 1267delG mutation in the AChR Ɛ subunit in nine members of two large Gipsy kindreds. Our observations indicate that founder Roma mutation 1267delG leads to a phenotype further characterized by ophthalmoplegia, bilateral ptosis, and good response to pyridostigmine and 3,4-DAP; but also by facial weakness, bulbar symptoms, neck muscle weakness, and proximal limb weakness that sometimes entails the loss of ambulation. Interestingly, we found in our series a remarkable proportion of patients with a progressive or fluctuating course of the disease. This finding is in some contrast with previous idea that considered this form of CMS as benign, non progressive, and with a low impact on the capacity of ambulation.

Long-term follow-up in patients with congenital myasthenic syndrome due to RAPSN mutations.

Rapsyn (RAPSN) mutations are a common cause of postsynaptic congenital myasthenic syndromes. We present a comprehensive description of the clinical and molecular findings of ten patients with CMS due to mutations in RAPSN, mostly with a long-term follow-up. Two patients were homozygous and eight were heterozygous for the common p.Asn88Lys mutation. In three of the heterozygous patients we have identified three novel mutations (c.869T > C; p.Leu290Pro, c.1185delG; p.Thr396Profs*12, and c.358delC; p.Gln120Serfs*8). In our cohort, the RAPSN mutations lead to a relatively homogeneous phenotype, characterized by fluctuating ptosis, occasional bulbar symptoms, neck muscle weakness, and mild proximal muscle weakness with exacerbations precipitated by minor infections. Interestingly, episodic exacerbations continue to occur during adulthood. These were characterized by proximal limb girdle weakness and ptosis, and not so much by respiratory insufficiency after age 6. All patients presented during neonatal period and responded to cholinergic agonists. In most of the affected patients, additional use of 3,4-diaminopyridine resulted in significant clinical benefit. The disease course is stable except for intermittent worsening.

The EGR2 gene is involved in axonal Charcot-Marie-Tooth disease.

BACKGROUND AND PURPOSE: A three-generation family affected by axonal Charcot-Marie-Tooth disease (CMT) was investigated with the aim of discovering genetic defects and to further characterize the phenotype. METHODS: The clinical, nerve conduction studies and muscle magnetic resonance images of the patients were reviewed. A whole exome sequencing was performed and the changes were investigated by genetic studies, in silico analysis and luciferase reporter assays. RESULTS: A novel c.1226G>A change (p.R409Q) in the EGR2 gene was identified. Patients presented with a typical, late-onset axonal CMT phenotype with variable severity that was confirmed in the ancillary tests. The in silico studies showed that the residue R409 is an evolutionary conserved amino acid. The p.R409Q mutation, which is predicted as probably damaging, would alter the conformation of the protein slightly and would cause a decrease of gene expression. CONCLUSIONS: This is the first report of an EGR2 mutation presenting as an axonal CMT phenotype with variable severity. This study broadens the phenotype of the EGR2-related neuropathies and suggests that the genetic testing of patients suffering from axonal CMT should include the EGR2 gene.

Targeted screening for the detection of Pompe disease in patients with unclassified limb-girdle muscular dystrophy or asymptomatic hyperCKemia using dried blood: A Spanish cohort.

We aimed to screen for Pompe disease in patients with unclassified limb-girdle muscular dystrophy (LGMD) or asymptomatic hyperCKemia using dried blood spot (DBS) assays. Subsequently, we aimed to calculate the diagnostic delay between initial symptom presentation and the diagnosis. A prospective, multicenter, observational study was conducted in 348 patients: 146 with unclassified LGMD and 202 with asymptomatic or paucisymptomatic hyperCKemia. We quantified levels of acid alpha-glucosidase (GAA) from dried blood spots analyzed fluorometrically. The test was positive in 20 patients, and Pompe disease was confirmed by genetic testing in 16. Undiagnosed Pompe disease was detected in 7.5% of patients with LGMD and in 2.5% of patients with persistent, idiopathic elevation of serum creatine kinase. The c.-32-13 T > G mutation was found most commonly. The diagnostic delay was 15 years on average. In conclusion, DBS tests are useful and reliable screening tools for Pompe disease. We recommend the dried blood spot test to be included in the diagnostic work-up of patients with unclassified myopathies with proximal weakness and/or hyperCKemia of unknown cause and, when positive, to define the diagnosis, it will have to be confirmed by biochemical and/or molecular genetic analysis.

Autoimmunity as a prognostic factor in sporadic adult onset cerebellar ataxia.

Cerebellar adult onset ataxia is a heterogeneous condition. The aim of this study was to ascertain if there is a heightened autoimmune background in patients with sporadic cerebellar ataxia of unknown origin, and if autoimmunity correlates with a more rapid evolution of the ataxia. We selected patients with sporadic progressive adult onset cerebellar ataxia with a follow-up of >5 years. As controls we included 43 patients with genetically demonstrated hereditary ataxia. All patients were tested for a panel of neuronal (onconeuronal, glutamate-decarboxylase [GAD], IgG/IgA transglutaminase 6 antibodies) and systemic non-neuronal antibodies (including IgG/IgA gliadin and transglutaminase 2, thyroperoxidase, thyroglobulin, antinuclear, striational, smooth muscle, mitochondrial, liver kidney microsomal, and parietal gastric cells antibodies). Correlation between the antibodies and disease progression was studied with Cox regression models and Kaplan-Meier plots. Forty-four patients were included. All patients were negative for onconeuronal or GAD antibodies. There were no significant differences between patients and controls in the prevalence of transglutaminase 6, 2, gliadin, or thyroid antibodies. However, when we studied the panel of systemic non-neuronal autoantibodies as a group, antibodies were more frequent in patients with sporadic ataxia (p = 0.018). The presence of one or more systemic non-neuronal antibodies correlated with a faster evolution to stage 2 (loss of independent gait) (p = 0.03) and shorter survival (p = 0.03) in patients with sporadic ataxia. We conclude that there is probably a heightened autoimmune background in some patients with sporadic cerebellar ataxia of unknown origin. The presence of systemic non-neuronal autoantibodies is a prognostic marker.

Spanish MYH7 founder mutation of Italian ancestry causing a large cluster of Laing myopathy patients.

Laing myopathy is a distal myopathy caused by mutations in the tail of the slow beta-myosin heavy chain gene MYH7. A large cluster of patients belonging to different families, with Laing myopathy due to p.K1729del mutation, was found in the Safor region, Spain. The same mutation was previously reported in an American family with Italian ancestry. The possibility that p.K1729del in MYH7 might be a founder mutation in the Safor patients and the chance of a common origin with the Italian-American family mutation was investigated by haplotype analyses, mutation data origin estimation and historical inquiry. Our results show that the p.K1729del in MYH7 harboured by patients from the Safor indeed is a founder mutation. A common ancestral origin of this mutation in the Spanish and Italian families is also suggested because they all share a core SNP haplotype at locus MYH7. Data estimation yields the origin of the mutation in the Safor at the beginning of the XVII century, when the Moorish were spelt and the region was resettled with Italian families.

[Guidelines for molecular diagnosis of Charcot-Marie-Tooth disease]. / Guía diagnóstica en el paciente con enfermedad de Charcot-Marie-Tooth.

INTRODUCTION: Charcot-Marie-Tooth disease (CMT) is the most frequent form of inherited neuropathy. In accordance with the inheritance pattern and degree of slowing of motor conduction velocity (MCV) of the median nerve, CMT encompasses five main forms: CMT1 (autosomal dominant [AD] or X-linked transmission and MCV < 38 m/s); CMT2 (AD or X-linked transmission and MCV > 38 m/s); CMT4 (autosomal recessive [AR] and severe slowing of MCV); AR-CMT2 (AR transmission and MCV > 38 m/s); and DI-CMT (intermediate form with AD transmission and MCV between 30 and 40 m/s). In spite of its stereotyped semiological repertoire (basically, symptoms and signs of sensory-motor polyneuropathy and pes cavus), CMT seems to be one of the most complex hereditary neurodegenerative syndromes, 31 causative genes having been cloned. DEVELOPMENT: This paper is aimed at performing a nosological review of the disease, emphasising the guidelines for its molecular diagnosis. Genetic epidemiological studies and genotypes reported in Spanish patients are revised. CONCLUSIONS: In the great majority of CMT cases, mutations involve a reduced number of genes, namely: for CMT1, PMP22, GJB1 and MPZ; for CMT2, MFN2 and GJB1; for CMT4, GDAP1, and NDRG1, HK1 and SH3TC2 (gypsies); for AR-CMT2, GDAP1; and for DI-CMT, GJB1 and MPZ. Given their low prevalence, mutations in other pathogenic genes should be investigated after discarding the previous ones. There is no place for the indiscriminate use of diagnostic CMT genetic panels.

Peripheral nerve hyperexcitability: a clinical and immunologic study of 38 patients.

OBJECTIVE: We studied a case series of peripheral nerve hyperexcitability (PNH) aiming to describe clinical characteristics, immunologic and cancer associations, antibodies against neuronal antigens (voltage-gated potassium channel antibodies [VGKC-Abs] and other), and muscle biopsy findings. METHODS: Patients presenting with clinical and electrophysiologic signs of PNH were selected. We studied clinical and electrophysiologic features; a panel of non-neuronal organ-specific antibodies, immunofluorescence on rat nervous tissues, and radioimmunoprecipitation for VGKC-Abs; and muscle biopsies. RESULTS: Thirty-eight patients were included. After the exclusion of 6 cases with axonopathy of known origin, patients were subdivided according to the presence of electrophysiologic findings of motor axonopathy and association with cancer: axonopathic-PNH (group A: 12 patients), isolated nonparaneoplastic PNH (group B: 16 patients), and isolated paraneoplastic PNH (3 with thymoma and myasthenia gravis, 1 with thyroid carcinoma). PNH clinical features were similar in groups A and B. We found an overall high prevalence of clinical autoimmunity (33% of group A and 63% of group B) and systemic non-neuronal autoantibodies (42% of group A and 75% of group B). However, VGKC-Abs were only positive in 2 patients of group B. Ten patients underwent muscle biopsy, which showed inflammatory changes in 2 cases and nonspecific myopathic features in 8. CONCLUSIONS: PNH is a heterogeneous disorder involving the peripheral nerves in patients with a high propensity for developing autoimmunity. Associated muscle diseases are frequent in the form of myositis, myasthenia gravis, or nonspecific myopathic pathologic findings. VGKC-Abs were uncommon in this series.

MYH7 gene tail mutation causing myopathic profiles beyond Laing distal myopathy.

OBJECTIVE: To describe a wide range of clinical and pathologic myopathic profiles associated with the p.K1729del mutation in the MYH7 gene, known to cause Laing distal myopathy. METHODS: A study conducted in the Safor region (Spain), setting of a large cluster of patients. Clinical, neurophysiologic, muscle imaging, and muscle biopsy studies and MYH7 gene sequencing were investigated in 32 patients from 4 kindreds. Data from 36 deceased or nonexamined patients were collected from hospital records or relatives. RESULTS: Onset ranged from congenital to the 6th decade. All patients presented weakness of great toe/ankle dorsiflexors and many had associated neck flexor, finger extensor, and mild facial weakness. In most cases, involvement of proximal and axial muscles was observed either clinically or by muscle imaging, sometimes giving rise to scapuloperoneal and limb-girdle syndromes. Disabling myalgias, skeletal deformities, and dilated cardiomyopathy in one patient were associated features. Life expectancy was not reduced but the spectrum of disability ranged from asymptomatic to wheelchair confined. Electromyographic neurogenic features were frequently recorded. Muscle fiber type disproportion, core/minicore lesions, and mitochondrial abnormalities were the most relevant pathologic alterations. All patients carried the p.K1729del mutation in MYH7. CONCLUSIONS: The p.K1729del mutation in the MYH7 gene expresses notable clinical variability and electromyographic and pathologic features that can lead to the misdiagnosis of neurogenic atrophies, congenital myopathies, or mitochondrial myopathies. Mutations in genes encoding other sarcomeric and reticulo-sarcoplasmic proteins involved in calcium regulation share pathologic characteristics with our patients, suggesting a possible pathogenetic connection.

EFNS guidelines on the diagnostic approach to pauci- or asymptomatic hyperCKemia.

OBJECTIVE: To provide evidence-based guidelines to general neurologists for the assessment of patients with pauci- or asymptomatic hyperCKemia. BACKGROUND: Recent epidemiologic studies show that up to 20% of 'normal' individuals have an elevated creatine kinase activity in the serum (sCK). The possibility of a subclinical myopathy is often raised, and patients may be unnecessarily denied treatment with statins. SEARCH STRATEGY: Electronic databases including Medline, the Cochrane Library and the American Academy of Neurology were searched for existing guidelines. Articles dealing with series of patients investigated for asymptomatic/pauci-symptomatic hyperCKemia and articles dealing with myopathies that can present with asymptomatic hyperCKemia were identified and reviewed. RESULTS: The only guidelines found were those approved by the Italian Association of Myology Committee, and the only relevant articles identified describe class IV studies. RECOMMENDATIONS: HyperCKemia needs to be redefined as values beyond 1.5 times the upper limit of normal (which itself needs to be appropriately defined). Pauci- or asymptomatic hyperCKemia with no apparent medical explanation may be investigated with a muscle biopsy if one or more of the following are present; the sCK is >or=3x normal, the electromyogram is myopathic or the patient is <25 years of age. In addition, women with sCK<3 times normal may be offered DNA testing because of the possibility of carrying a dystrophin mutation.