Treatment outcome in juvenile-onset myasthenia gravis.

INTRODUCTION: Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction. Approximately 10%-15% of MG patients have juvenile (<18 years of age) onset. We aimed to assess the clinical course, outcome, and subjectively perceived health status of a cohort of juvenile MG patients. METHODS: This was a retrospective analysis of medical records of 101 patients followed by a cross-sectional questionnaire study. RESULTS: The mean age of patients was 12.8 years at onset and 13.7 years at diagnosis. Ninety percent of the patients were seropositive. Over 40% of the patients were treated with immunosuppression and over 80% underwent thymectomy. The mean Myathenia Gravis Activities of Daily Living (MG-ADL) scale score was 2.48. At last follow-up, 30.9% of patients were in complete, stable remission; 77.8% perceived their health as good. DISCUSSION: The treatment outcome for juvenile MG is favorable, with a marked reduction of symptoms and good day-to-day activity achieved for most patients. Muscle Nerve 59:549-549, 2019.

Are electrophysiological criteria useful in distinguishing childhood demyelinating neuropathies?

Childhood chronic inflammatory demyelinating polyneuropathy (CIDP) needs to be differentiated from hereditary neuropathy. We aimed to validate existing CIDP nerve conduction study (NCS) criteria in a group of children with demyelinating neuropathies of chronic or subacute onset. Retrospective analysis of clinical and NCS results in 18 children with CIDP, 7 with hereditary neuropathy with pressure palsy (HNPP), and 24 with Charcot-Marie-Tooth 1a (CMT1a). AAN and EFNS electrodiagnostic CIDP criteria were fulfilled in 17 of 18 CIDP, 3 of 7 HNPP, and 23 of 24 CMT1a patients. A distal compound muscle action potential (dCMAP) of >9 ms was observed in 14 of 18 CIDP patients but not in any patients with HNPP. Abnormal median/normal sural SNAP (AMNS) and a 10 m/s difference between conduction velocities (CV) of two corresponding nerves were not observed in any CMT1a patients. NCS in CMT1a, HNPP, and CIDP reflect demyelination. dCMAP duration, sensory AMNS, and a 10 m/s CV difference parameter are most useful in the differential diagnosis of pediatric CIDP.

The Frequency of c.550delA Mutation of the CANP3 Gene in the Polish LGMD2A Population.

BACKGROUND: Limb girdle muscular dystrophy 2A (LGMD2A) is the most frequent LGMD variant in the European population, representing about 40% of LGMD. The c.550delA mutation in the CANP3 (calcium activated neutral protease 3) gene is the most commonly reported mutation in LGMD2A. Prevalence of this mutation in the Polish population has not been previously investigated. The aim of this study was to identify and estimate the frequency of the c.550delA mutation in Polish LGMD2A patients. METHODS: Polymerase chain reaction-sequencing analysis, restriction fragment length polymorphism polymerase chain reaction method. RESULTS: We analyzed 76 families affected with LGMD and identified 62 probands with mutations in the CANP3 gene. C.550delA was the most common mutation identified, being found in 78% of the LGMD2A families. The remaining mutations observed multiple times were as follows: c.598-612del15ntd; c.2242C>T; c.418dupC; c.1356insT, listed in terms of decreasing frequency. Two novel variants in the CANP3 gene, that is, c.700G>A Gly234Arg and c.661G>A Gly221Ser were also characterized. Overall, mutations in the LGMD2A gene were estimated to be present in 81% of patients with the LGMD phenotype who were without sarcoglycans and dysferlin deficiency on immunocytochemical analysis. The frequency of the heterozygous c.550delA mutation in the healthy Polish population was estimated at 1/124. CONCLUSIONS: The c.550delA is the most frequent CANP3 mutation in the Polish population, thus sequencing of exon 4 of this gene could identify the majority of LGMD2A patients in Poland.

Motor unit loss estimation by the multipoint incremental MUNE method in children with spinal muscular atrophy--a preliminary study.

Quantitative EMG reflects denervation of muscles after lower motor neuron degeneration in spinal muscular atrophy (SMA) but does not reflect actual motor unit loss. The aim of our study was to assess the value of the multipoint incremental motor unit number estimation (MUNE) method in the modification by Shefner in estimating motor unit loss in SMA. The number of motor units, the mean amplitude of an average surface-detected single motor unit potential (SMUP), and the amplitude of compound motor action potentials (CMAP) were estimated in 14 children with SMA in the abductor pollicis brevis (ABP). Significant differences in MUNE values and SMUP and CMAP amplitude were found between the SMA and control groups (P < 0.0001). MUNE values correlated with Hammersmith Functional Motor Scale (HFMS) scores (P < 0.05). Increased SMUP amplitude values correlated with decreased HFMS scores (P < 0.05). The study confirms that MUNE method in the modification by Shefner is a useful tool reflecting motor unit loss in SMA, and it is easy to perform and well tolerated. MUNE and SMUP amplitude seemed to be sensitive parameters reflecting motor dysfunction in SMA but a longitudinal study in a larger number of subjects is needed.

Early-onset facioscapulohumeral muscular dystrophy type 1 with some atypical features.

Facioscapulohumeral muscular dystrophy cases with facial weakness before the age of 5 and signs of shoulder weakness by the age of 10 are defined as early onset. Contraction of the D4Z4 repeat on chromosome 4q35 is causally related to facioscapulohumeral muscular dystrophy type 1, and the residual size of the D4Z4 repeat shows a roughly inverse correlation with the severity of the disease. Contraction of the D4Z4 repeat on chromosome 4q35 is believed to induce a local change in chromatin structure and consequent transcriptional deregulation of 4qter genes. We present early-onset cases in the Polish population that amounted to 21% of our total population with facioscapulohumeral muscular dystrophy. More than 27% of them presented with severe phenotypes (wheelchair dependency). The residual D4Z4 repeat sizes ranged from 1 to 4 units. In addition, even within early-onset facioscapulohumeral muscular dystrophy type 1 phenotypes, some cases had uncommon features (head drop, early disabling contractures, progressive ptosis, and respiratory insufficiency and cardiomyopathy).

Novel point mutations in survival motor neuron 1 gene expand the spectrum of phenotypes observed in spinal muscular atrophy patients.

The aim of our study was to identify point mutations in a group of 606 patients diagnosed for spinal muscular atrophy with excluded biallelic loss of the SMN1 gene. Point missense mutations or small deletions in the SMN1 gene were ultimately identified in 18 patients. Six patients were found to have small deletions, the c.429_435del mutation in 3 cases, the c.431delC mutation in 2 and c.722delC in one. Those mutations, not described previously, were characteristic of patients presenting a severe phenotype. The most frequent missense mutation - p.Thr274Ile, was identified in 9 patients presenting a rather mild phenotype. Three other missense mutations, i.e., p.Ser230Leu, p.Ala111Gly and p.Pro244Leu, were identified in a further 3 SMA3 patients. Mutation p.Pro244Leu, not described so far, was identified in a patient with a mild form of SMA and more distal distribution of muscle weakness. Our results suggest a specific point mutation spectrum in the Polish population. The existence of small deletions not identified thus far could suggest a possible founder effect. In patients with preserved one SMN1 allele without common exon 7 deletion, presenting a mild form of SMA, a special consideration should be given to the p.Thr274Ile mutation.

Clinical, electrophysiological, and molecular findings in early onset hereditary neuropathy with liability to pressure palsy.

INTRODUCTION: The first episode of hereditary neuropathy with liability to pressure palsy (HNPP) in childhood is rare. METHODS: We analyzed retrospectively the data of 7 patients with a deletion in PMP22 and onset of symptoms before age 18 years. Direct sequencing of the LITAF (lipopolysaccharide-induced tumor necrosis factor) gene was performed in patients and family members. RESULTS: Clinical presentations varied from mononeuropathies to brachial plexopathy, with recurrent episodes in 4 patients. Electrophysiological abnormalities characteristic for HNNP were found in most subjects. Analysis of the LITAF gene revealed an Ile92Val polymorphism in 6 of 7 (86%) probands and 5 of 7 (83%) family members, over 4 times greater frequency than in the general population. CONCLUSIONS: Clinical suspicion of HNPP even when nerve conduction study results do not fulfill HNPP criteria should indicate genetic testing. In our patients, early-onset HNPP was associated frequently with isoleucine92valine LITAF polymorphism.

Carpal tunnel syndrome in children.

Carpal tunnel syndrome rarely occurs in children. We retrospectively analyzed clinical data of 11 patients aged 5-17 diagnosed with carpal tunnel syndrome at a single pediatric neuromuscular center. Nerve conduction studies were performed according to the American Association of Electrodiagnostic Medicine recommendations. Additional imaging tests of the wrist were performed in 10 patients. In our group of 11 children, carpal tunnel syndrome was idiopathic in only 1 case. In the remaining subjects, it was secondary to congenital bone anomaly (6), hypothyroidism (2), or myopathic contractures (1). In 1 case, metabolic workup revealed an underlying mucopolysaccharidosis. Our results confirm that idiopathic carpal tunnel syndrome is rare in children. Hand clumsiness and thenar hypoplasia rather than sensory complaints are the presenting symptoms. Whenever carpal tunnel syndrome is diagnosed in a child, a thorough differential diagnosis should be made because of the secondary nature of this disease in most pediatric patients.

Two pathogenic mutations located within the 5'-regulatory sequence of the GJB1 gene affecting initiation of transcription and translation.

In contrast to mutations in the coding sequences of a genes involved in the pathogenesis of Charcot-Marie-Tooth disease (CMT), little is known about CMT phenotypes resulting from a DNA variants located in regulatory sequences of a given " CMT gene". Charcot-Marie-Tooth type X1 disease (CMTX1) is caused by mutations in the GJB1 gene coding for an ion channel known as connexin, with a molecular mass of 32 kDa (Cx32). Only 0.01% of the GJB1 gene mutations have been reported in its 5' regulatory sequence. Pathogenic mutations occured in the internal ribosome entry site (IRES) are extremely rarely reported in human genetic disorders. To the best of our knowledge, in this study we report for the first time in an Eastern European population, two CMTX1 families in which two pathogenic mutations in the 5' regulatory sequence of the GJB1 gene (c.-529T>C and -459C>T) have been found. The two mutations identified in our study disturb the 5' UTR sequence in two different ways, by affecting the transcription factor SOX10 binding site (c.-529T>C) and by the disrupting IRES element of GJB1 gene (c.-459C>T). These regions are responsible for transcription (SOX10) and initiation of translation (IRES), respectively. On the basis of our findings that, in contrast to the most DNA sequence variants reported in untranslated regulatory regions of genes, the c.-459C>T and c.-529T>C mutations remain pathogenic in the context of different ethnic background.

L239F founder mutation in GDAP1 is associated with a mild Charcot-Marie-Tooth type 4C4 (CMT4C4) phenotype.

Over 40 mutations in the GDAP1 gene have been shown to segregate with Charcot-Marie-Tooth disease (CMT). Among these, only two mutations, i.e., S194X and Q163X have been reported in a sufficient number of CMT families to allow for the construction of reliable phenotype-genotype correlations. Both the S194X and Q163X mutations have been shown to segregate with an early-onset and severe neuropathy resulting in loss of ambulance at the beginning of the second decade of life. In this study, we identified the L239F mutation in the GDAP1 gene in one Bulgarian and five Polish families. We hypothesized that the L239F mutation may result from a founder effect in the European population since this mutation has previously been reported in Belgian, Czech, and Polish patients. In fact, we detected a common disease-associated haplotype within the 8q13-q21 region in the Polish, German, Italian, Czech, and Bulgarian CMT families. Like the previously detected "regional" S194X and Q163X mutations, respectively present in Maghreb countries and in patients of Spanish descent, the L239F mutation seems to be the most common GDAP1 pathogenic variant in the Central and Eastern European population. Given the likely presence of a common ancestor harboring the L239F mutation, we decided to compare the phenotypes of the CMT (L239F) patients collected in this study with those of previously reported cases. In contrast to CMT4A caused by the S194X and Q163X mutations, the CMT phenotype resulting from the L239F substitution represents a milder clinical entity with a long-preserved period of ambulance at least until the end of the second decade of life.

[Detection of rare mutations in the dystrophin gene]. / Wykrywanie rzadkich mutacji w genie dystrofiny.

INTRODUCTION: Duchenne/Becker muscular dystrophies (DMD/BMD) are allelic X-linked, recessive proximal muscle disorders, caused by mutations in the dystrophin gene located in Xp21. DMD occurs with the incidence 1:3500, BMD with the incidence of 1:18,500 new-born males. Approximately about 60% of mutations in the dystrophin gene are deletions, 10%--duplications and 30%--point mutations. AIM: The aim of the study was detection of the mutations: rare deletions, duplications and point mutations in the dystrophin gene in patients diagnosed as DMD/BMD in whom the presence of the most common deletions had previously been excluded. MATERIALS AND METHODS: Molecular analysis was performed using DNA samples isolated from 105 DMD and 10 BMD patients. Detection of rare deletions and duplications was carried out by Multiplex Ligation-dependent Probe Amplification (MLPA). Point mutations were identified by analysis of single strand conformation polymorphism (SSCP) and DNA sequencing. RESULTS: 38 Different mutations were detected: 10 rare deletions, 14 duplications and 14 point mutations and microdeletions. Majority of the detected rare deletions (7 out of 10) and point mutations (11 out of 14) are novel mutations. CONCLUSIONS: Application of MLPA technique allows the detection of small, rare deletions and duplications. Identification of the nature and localization of the mutations may, in the future, help to apply appropriate therapeutic approaches in DMD patients.

A patient with both Charcot-Marie-Tooth disease (CMT 1A) and mild spinal muscular atrophy (SMA 3).

In the present study, we report a single Polish SMA family in which the 17p11.2-p12 duplication causative for the Charcot-Marie-Tooth type 1A disease (CMT1A) was found in addition to a deletion of exons 7 and 8 of the SMN1 gene. A patient harboring both SMA and CMT1A mutations manifested with SMA3 phenotype and foot deformity. Her electrophysiological testing showed chronic neurogenic changes in proximal muscles that are typical for SMA, but also slowed conduction velocity in motor and sensory fibers that is typical for demyelinating neuropathy.

Multi-minicore myopathy: a clinical and histopathological study of 17 cases.

Multi-minicore disease (MmD) is a congenital myopathy morphologically defined by the multifocal lack of oxidative activity on light microscopy (LM) and multiple small zones of sarcomeric disorganization on electron microscopy (EM) as the main findings in muscle biopsy. We report on clinical and pathomorphological features of 17 patients diagnosed with multi-minicore myopathy at our department. Clinically, axial and proximal muscle weakness was the predominant distinguishing feature. Dysmorphic features such as high-arched palate and chest deformities were frequent findings. Limitation in cervical spine mobility was found in 4 cases. Most of our cases were slowly progressive but three fatal cases also occurred. Multifocal lack of oxidative activity was found in 16/22 biopsies on LM. Examination on EM enabled the final diagnosis of MmD in all cases. It is of special interest that in 3 patients fulfilling the criteria of pure congenital fibre type disproportion and in 2 cases of centronuclear myopathy, the findings of ultrastructural examination led us to a revised diagnosis of MmD. We postulate that all muscle biopsies with abnormal fibre proportion or centrally located nuclei as the only pathology on LM need to undergo careful EM evaluation to identify possible underlying multi-minicore disease.

Is a novel I214M substitution in the NEFL gene a cause of Charcot-Marie-Tooth disease? Functional analysis using cell culture models.

Recent studies have shown that mutations in neurofilament light subunit gene (NEFL) cause Charcot-Marie-Tooth (CMT) disease. Since the first description of the Gln333Pro mutation in the NEFL gene, 10 pathogenic mutations in the NEFL gene have been reported in patients affected with CMT disease. We report a novel I214M amino acid substitution in the NEFL gene in two unrelated patients affected with CMT. Because the I214M amino acid substitution in the NEFL protein was not detected in a CMT affected brother of the proband, its pathogenic effect became unclear. In order to determine whether this amino acid substitution is a benign polymorphism or causative of the disease, we performed a functional analysis of the mutant I214M neurofilament protein (NFL). Transfections of the mutant protein in cultured cells revealed an increased tendency to form highly compacted filamentous structures but no other alterations of neurofilament assembly or transport were observed. Furthermore, the sibling of one of the patients was also affected with CMT but did not have the I214M substitution. These data suggest that this I214M substitution in the NEFL gene was not a direct cause of the disease but could be a polymorphism or possibly a modifier of the CMT phenotype.

MFN2 mutation distribution and genotype/phenotype correlation in Charcot-Marie-Tooth type 2.

Mutations in mitofusin 2 (MFN2) have been reported in Charcot-Marie-Tooth type 2 (CMT2) families. To study the distribution of mutations in MFN2 we screened 323 families and isolated patients with distinct CMT phenotypes. In 29 probands, we identified 22 distinct MFN2 mutations, and 14 of these mutations have not been reported before. All mutations were located in the cytoplasmic domains of the MFN2 protein. Patients presented with a classical but rather severe CMT phenotype, since 28% of them were wheelchair-dependent. Some had additional features as optic atrophy. Most patients had an early onset and severe disease status, whereas a smaller group experienced a later onset and milder disease course. Electrophysiological data showed in the majority of patients normal to slightly reduced nerve conduction velocities with often severely reduced amplitudes of the compound motor and sensory nerve action potentials. Examination of sural nerve specimens showed loss of large myelinated fibres and degenerative mitochondrial changes. In patients with a documented family history of CMT2 the frequency of MFN2 mutations was 33% indicating that MFN2 mutations are a major cause in this population.

A novel Met116Thr mutation in the GDAP1 gene in a Polish family with the axonal recessive Charcot-Marie-Tooth type 4 disease.

Mutations in the gene coding for ganglioside-induced differentiation-associated protein-1 (GDAP1), which maps to chromosome 8q21, have been described in families with autosomal recessive Charcot-Marie-Tooth disease (CMT4A). Interestingly, some mutations in the GDAP1 gene have been reported in the demyelinating form of CMT1 disease, whereas others were found in patients with the axonal type of CMT disease. So far, 23 mutations in the GDAP1 gene have been reported in patients of different ethnic origins. In this study we report a novel mutation Met116Thr in the GDAP1 gene identified in a three generation Polish family with axonal CMT4.

Application of a rapid non-invasive technique in the molecular diagnosis of spinal muscular atrophy (SMA).

BACKGROUND AND PURPOSE: Proximal spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by mutations of the SMN1 gene. The most frequent mutation is biallelic deletion of exon 7 of the SMN1 gene. A small percentage of SMA patients present compound heterozygosity with a point mutation on one allele and deletion on the other. In the remaining cases the disease is unlikely to be related to SMN1 defects. The aim of our study was to estimate the frequency of the common biallelic exon 7 SMN1 deletion in our Polish SMA cohort and implement a test for assessing a molecular defect at the SMN1 locus versus defects in the other genes. MATERIAL AND METHODS: The molecular analysis was performed in a group of 269 patients fulfilling diagnostic criteria of the International SMA Consortium. The common SMN1 exon 7 deletion was tested by a standard PCR analysis. Patients lacking the common mutation were subsequently analyzed for a number of SMN1 alleles with a quantitative test based on real-time PCR. RESULTS: The frequency of homozygous loss of exon 7 in the SMN1 gene was 96.6% (260/269) in our Polish SMA cohort. In 5 of 9 non-deleted patients the real-time PCR analysis showed a decreased number of SMN1 copies. We anticipate that the non-deleted allele carries a second mutation in SMN1 which may contribute to the pathogenesis of SMA. We have also identified 4 patients (1.5%) with SMA carrying two SMN1 alleles without the exon 7 deletion. CONCLUSIONS: The molecular analysis of the biallelic exon 7 of the SMN1 deletion is a standard and reliable test in cases of SMA. Introduction of a quantitative test based on "real-time PCR" further enhances the diagnostic potential by increasing the detection rate of cases likely to be caused by point mutation of the SMN1 gene.

[Genetic investigations in facioscapulohumeral muscular dystrophy: a preliminary report]. / Badania genetyczne w dystrofii twarzowo-lopatkowo-ramieniowej--doniesienie wstepne.

Facioscapulohumeral muscular dystrophy (FSHD) is a primary muscle disorder with autosomal dominant inheritance. FSHD was mapped to chromosome 4 locus q35, but the gene is not yet known. It is characterised by progressive, often asymmetric, selective muscular weakness and great clinical variability. The aim of the study was to analyze 62 FSHD cases from 44 Polish families in which the diagnosis was confirmed by DNA analyses. FSHD diagnosis was based on the clinical findings and standardized investigations confirming primary muscular involvement (EMG, muscle biopsy). DNA analysis was based on EcoRI/BlnI restriction enzyme digestion followed by hybridization with P13E-11 molecular probe. In our material, we have found a relatively large percentage (41%) of big deletions (EcoRI/BlnI fragment of 10-15 kb [kilo bases]), which in the majority of cases (67%) was present in isolated cases. In 10 families (23%) the phenotype was assessed as severe. These are cases with the onset before the age of 10 and fast progression. "Middle sized" deletions (EcoRI/BlnI fragment of 16-29 kb) were prevalent in familial cases and present in 57% of families. "Small" deletion was found in one family (EcoRI/BlnI fragment of 30 kb). Somatic mosaicism was confirmed in one case. De novo mutations were shown in 11% of the examined families. The results of this study indicate that the bigger the deletion, the more severe the FSHD course, however there are some exceptions. A similar relationship has been shown by previous research. Molecular analyses are particularly important in atypical and sporadic cases. It is the first genetic presentation of a group of patients' with this kind of dystrophy in the Polish population.