Clinical and functional characterization of a long survivor congenital titinopathy patient with a novel metatranscript-only titin variant.

Congenital titinopathies are an emerging group of a potentially severe form of congenital myopathies caused by biallelic mutations in titin, encoding the largest existing human protein involved in the formation and stability of sarcomeres. In this study we describe a patient with a congenital myopathy characterized by multiple contractures, a rigid spine, non progressive muscular weakness, and a novel homozygous TTN pathogenic variant in a metatranscript-only exon: the c.36400A > T, p.Lys12134*. Muscle biopsies showed increased internalized nuclei, variability in fiber size, mild fibrosis, type 1 fiber predominance, and a slight increase in the number of satellite cells. RNA studies revealed the retention of intron 170 and 171 in the open reading frame, and immunoflourescence and western blot studies, a normal titin content. Single fiber functional studies showed a slight decrease in absolute maximal force and a cross-sectional area with no decreases in tension, suggesting that weakness is not sarcomere-based but due to hypotrophy. Passive properties of single fibers were not affected, but the observed increased calcium sensitivity of force generation might contribute to the contractural phenotype and rigid spine of the patient. Our findings provide evidence for a pathogenic, causative role of a metatranscript-only titin variant in a long survivor congenital titinopathy patient with distal arthrogryposis and rigid spine.

Respiratory muscle involvement in HNRNPDL LGMD D3 muscular dystrophy: an extensive clinical description of the first Italian patient.

Limb girdle muscular dystrophy is a genetically inherited condition that primarily affects skeletal muscle leading to progressive, predominantly proximal muscle weakness at presentation. Autosomal dominant LGMD represent 10% of all LGMDs. HNRNPDL-related muscular dystrophy, LGMD1G/LGMD D3 (MIM#609115), is an extremely rare autosomal dominant adult onset myopathy described in a handful of families. Here we fully characterized the muscular and respiratory involvement of a 58 years old Italian woman presenting the previously reported pathogenic variant c.1132G > C p.(Asp378Asn) in the HNRNPDL gene.

A new congenital multicore titinopathy associated with fast myosin heavy chain deficiency.

Congenital titinopathies are myopathies with variable phenotypes and inheritance modes. Here, we fully characterized, using an integrated approach (deep phenotyping, muscle morphology, mRNA and protein evaluation in muscle biopsies), two siblings with congenital multicore myopathy harboring three TTN variants predicted to affect titin stability and titin-myosin interactions. Muscle biopsies showed multicores, type 1 fiber uniformity and sarcomeric structure disruption with some thick filament loss. Immunohistochemistry and Western blotting revealed a marked reduction of fast myosin heavy chain isoforms. This is the first observation of a titinopathy suggesting that titin defect leads to secondary loss of fast myosin heavy chain isoforms.

Airway clearance techniques in neuromuscular disorders: A state of the art review.

This is a unique state of the art review written by a group of 21 international recognized experts in the field that gathered during a meeting organized by the European Neuromuscular Centre (ENMC) in Naarden, March 2017. It systematically reports the entire evidence base for airway clearance techniques (ACTs) in both adults and children with neuromuscular disorders (NMD). We not only report randomised controlled trials, which in other systematic reviews conclude that there is a lack of evidence base to give an opinion, but also include case series and retrospective reviews of practice. For this review, we have classified ACTs as either proximal (cough augmentation) or peripheral (secretion mobilization). The review presents descriptions; standard definitions; the supporting evidence for and limitations of proximal and peripheral ACTs that are used in patients with NMD; as well as providing recommendations for objective measurements of efficacy, specifically for proximal ACTs. This state of the art review also highlights how ACTs may be adapted or modified for specific contexts (e.g. in people with bulbar insufficiency; children and infants) and recommends when and how each technique should be applied.

New Survival Target for Duchenne Muscular Dystrophy.

We report a patient with a typical phenotype and clinical history of Duchenne muscular dystrophy who is currently 53 years old. Because of improvements in cardiopulmonary care, there has been a great improvement in survival and preservation of quality of life for many of these patients. Whereas it is no longer rare to find patients with Duchenne muscular dystrophy living into their fifth decade, this is the first report of a patient in his sixth decade of life. We believe that besides use of continuous noninvasive respiratory support, the fortuitous absence of dilated cardiomyopathy associated with the particular point mutation of his dystrophin gene has permitted prolonged survival.

Allogeneic mesenchymal stem cell therapy outcomes for three patients with spinal muscular atrophy type 1.

No effective medical treatment has been documented for spinal muscular atrophy; however, cellular, molecular, and preclinical studies suggest that allogenic mesenchymal stem cells may play a role. Three children with spinal muscular atrophy type 1 underwent multiple intrathecal and intravenous infusions of mesenchymal stem cells. Their pretreatment, treatment, and posttreatment physical function were quantitated by the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders scale for two patients and documented by video for all three. Infant Test of Neuromuscular Disorders values were 3 before treatment, 10 and 16 during treatment, and 0 and 10 seven and twelve months after treatment was discontinued, respectively. No adverse effects have been noted for at least 44 and 49 mos from onset of treatment, respectively. These data represent the first objective, quantifiable improvements in physical function for any treatment of spinal muscular atrophy. Although the benefits were lost when the therapy was withdrawn, this may be an initial step in establishing mesenchymal stem cells as a safe and effective treatment of spinal muscular atrophy.

Prevalence of congenital muscular dystrophy in Italy: a population study.

OBJECTIVE: We provide a nationwide population study of patients with congenital muscular dystrophy in Italy. METHODS: Cases were ascertained from the databases in all the tertiary referral centers for pediatric neuromuscular disorders and from all the genetic diagnostic centers in which diagnostic tests for these forms are performed. RESULTS: The study includes 336 patients with a point prevalence of 0.563 per 100,000. Mutations were identified in 220 of the 336 (65.5%). The cohort was subdivided into diagnostic categories based on the most recent classifications on congenital muscular dystrophies. The most common forms were those with α-dystroglycan glycosylation deficiency (40.18%) followed by those with laminin α2 deficiency (24.11%) and collagen VI deficiency (20.24%). The forms of congenital muscular dystrophy related to mutations in SEPN1 and LMNA were less frequent (6.25% and 5.95%, respectively). CONCLUSIONS: Our study provides for the first time comprehensive epidemiologic information and point prevalence figures for each of the major diagnostic categories on a large cohort of congenital muscular dystrophies. The study also reflects the diagnostic progress in this field with an accurate classification of the cases according to the most recent gene discoveries.

Duchenne muscular dystrophy: life prolongation by noninvasive ventilatory support.

OBJECTIVE: American, Japanese, and Canadian centers have demonstrated that noninvasive intermittent positive pressure ventilatory support (NVS) can be used continuously and in the long-term by people with Duchenne muscular dystrophy as a definitive alternative to tracheostomy mechanical ventilation. The aim of this study was to report this for the first time in Europe. DESIGN: In this study, more than 300 patients with Duchenne muscular dystrophy were followed. End-tidal carbon dioxide, oxyhemoglobin saturation, and vital capacity were measured at each visit. Of the 300 patients, 79 used NVS for 8 hrs or more per day and 20 of these became continuously dependent on NVS. RESULTS: A total of 20 patients have continuously depended on NVS for survival, for a total of 336 patient-years, up to 16 yrs in one case. Nocturnal NVS was begun for symptomatic hypoventilation when the vital capacity had decreased to a mean of 831 ± 173 ml, and continuous dependence on NVS was necessary when the vital capacity had decreased below 297 ± 113 ml. CONCLUSIONS: Noninvasive respiratory management can prolong survival without resorting to tracheotomy and without hospitalization.

Mutations in the N-terminal actin-binding domain of filamin C cause a distal myopathy.

Linkage analysis of the dominant distal myopathy we previously identified in a large Australian family demonstrated one significant linkage region located on chromosome 7 and encompassing 18.6 Mbp and 151 genes. The strongest candidate gene was FLNC because filamin C, the encoded protein, is muscle-specific and associated with myofibrillar myopathy. Sequencing of FLNC cDNA identified a c.752T>C (p.Met251Thr) mutation in the N-terminal actin-binding domain (ABD); this mutation segregated with the disease and was absent in 200 controls. We identified an Italian family with the same phenotype and found a c.577G>A (p.Ala193Thr) filamin C ABD mutation that segregated with the disease. Filamin C ABD mutations have not been described, although filamin A and filamin B ABD mutations cause multiple musculoskeletal disorders. The distal myopathy phenotype and muscle pathology in the two families differ from myofibrillar myopathies caused by filamin C rod and dimerization domain mutations because of the distinct involvement of hand muscles and lack of pathological protein aggregation. Thus, like the position of FLNA and B mutations, the position of the FLNC mutation determines disease phenotype. The two filamin C ABD mutations increase actin-binding affinity in a manner similar to filamin A and filamin B ABD mutations. Cell-culture expression of the c.752T>C (p.Met251)Thr mutant filamin C ABD demonstrated reduced nuclear localization as did mutant filamin A and filamin B ABDs. Expression of both filamin C ABD mutants as full-length proteins induced increased aggregation of filamin. We conclude filamin C ABD mutations cause a recognizable distal myopathy, most likely through increased actin affinity, similar to the pathological mechanism of filamin A and filamin B ABD mutations.

Spastic paraplegia with thinning of the corpus callosum and white matter abnormalities: further mutations and relative frequency in ZFYVE26/SPG15 in the Italian population.

Spastic paraplegia with thinning of the corpus callosum (ARHSP-TCC) is a relatively frequent form of complicated hereditary spastic paraplegia in which mental retardation and muscle stiffness at onset are followed by slowly progressive paraparesis and cognitive deterioration. Although genetically heterogeneous, ARHSP-TCC is frequently associated with mutations in the SPG11 gene, on chromosome 15q. However, it is becoming evident that ARHSP-TCC can also be the clinical presentation of mutations in ZFYVE26 (SPG15), as shown by the recent identification of eight families with a variable phenotype. Here, we present an additional Italian ARHSP-TCC patient harboring two new, probably loss-of-function mutations in ZFYVE26. This finding, together with the report of a mutation in another Italian family, provides confirmation that ZFYVE26 is the second gene responsible for ARHSP-TCC in the Italian population.

Daily salbutamol in young patients with SMA type II.

The aim of this open pilot study was to establish the profile of tolerability and clinical response of salbutamol (albuterol) in a cohort of young children affected by type II spinal muscular atrophy (SMA). Twenty-three children between 30 months and 6 years of age were treated with salbutamol (2 mg three times a day) for 1 year. All children were longitudinally assessed using the Hammersmith motor functional scale 6 months before treatment started (T0), at baseline (T1) and 6 and 12 months later. There was no significant change in function between T0 and T1 assessments, but the functional scores recorded after 6 and 12 months of treatment were significantly higher than those recorded at baseline (p=0.006). Our results suggest that salbutamol may be beneficial to SMA patients without producing any major side effect. Larger prospective randomized, double-blind, placebo controlled trials are needed to confirm these preliminary findings.

Phenylbutyrate increases SMN expression in vitro: relevance for treatment of spinal muscular atrophy.

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease, characterized by degeneration of the anterior horn cells of the spinal cord. SMA presents with a highly variable phenotype ranging from very severe to mild (type I-III). No cure for SMA is available at present. All forms of SMA are caused by homozygous loss of the functional survival motor neuron (SMN1) gene. However, all patients have one or more copies of the SMN2 gene, nearly identical to SMN1. Both genes encode the SMN protein but the level produced by SMN2 is insufficient to protect from disease. Increasing SMN2 gene expression could be of considerable therapeutic importance. The aim of this study was to assess whether SMN2 gene expression can be increased by 4-phenylbutyrate (PBA). Fibroblast cell cultures from 16 SMA patients affected by different clinical severities were treated with PBA, and full-length SMN2 transcripts were measured by real-time PCR. In all cell cultures, except one, PBA treatment caused an increase in full-length SMN2 transcripts, ranging from 50 to 160% in type I and from 80 to 400% in type II and III cultures. PBA was found also effective in enhancing SMN protein levels and the number of SMN-containing nuclear structures (gems). These data show that SMN expression is considerably increased by PBA, and suggest that the compound, owing also to its favorable pharmacological properties, could be a good candidate for the treatment of SMA.

Nerve growth factor expression in human dystrophic muscles.

Nerve growth factor (NGF) is a neurotrophin that is expressed during muscle development and is also capable of favoring muscle regeneration in experimental studies. The presence of NGF in muscular dystrophies, such as Duchenne and Becker muscular dystrophies, has never been fully explored. By means of immunohistochemistry, we show that regenerating muscle fibers from such patients consistently express NGF, as do myofibroblasts and mast cells. By contrast, rest fibers from dystrophic patients, as well as muscle fibers from healthy, control patients and even regenerative muscle fibers in polymyositis do not show NGF immunoreactivity. The paracrine effect of NGF on muscle regeneration, as well as its chemoattractant capacities for mast cells, may contribute to explaining why regenerating fibers most frequently occur in clusters and why mast cells are more numerous in dystrophic muscles. Moreover, being a mediator of wound healing and tissue fibrosis, NGF may contribute to long-term muscle regeneration impairment by tissue fibrosis in the muscular dystrophies.

Mutations of the selenoprotein N gene, which is implicated in rigid spine muscular dystrophy, cause the classical phenotype of multiminicore disease: reassessing the nosology of early-onset myopathies.

Multiminicore disease (MmD) is an autosomal recessive congenital myopathy characterized by the presence of multiple, short core lesions (known as "minicores") in most muscle fibers. MmD is a clinically heterogeneous condition, in which four subgroups have been distinguished. Homozygous RYR1 mutations have been recently identified in the moderate form of MmD with hand involvement. The genes responsible for the three other forms (including the most prevalent phenotype, termed the "classical" phenotype) remained, so far, unknown. To further characterize the genetic basis of MmD, we analyzed a series of 62 patients through a combined positional/candidate-gene approach. On the basis of clinical and morphological data, we suspected a relationship between classical MmD and the selenoprotein N gene (SEPN1), which is located on chromosome 1p36 (RSMD1 locus) and is responsible for the congenital muscular dystrophy with rigid spine syndrome (RSMD). A genomewide screening, followed by the analysis of 1p36 microsatellite markers in 27 informative families with MmD, demonstrated linkage to RSMD1 in eight families. All showed an axial myopathy with scoliosis and respiratory failure, consistent with the most severe end of the classical MmD spectrum; spinal rigidity was evident in some, but not all, patients. We excluded linkage to RSMD1 in 19 families with MmD, including 9 with classical MmD. Screening of SEPN1 in the 8 families that showed linkage and in 14 patients with classical sporadic disease disclosed 9 mutations affecting 17 patients (12 families); 6 were novel mutations, and 3 had been described in patients with RSMD. Analysis of three deltoid biopsy specimens from patients with typical RSMD revealed a wide myopathological variability, ranging from a dystrophic to a congenital myopathy pattern. A variable proportion of minicores was found in all the samples. The present study represents the first identification of a gene responsible for classical MmD, demonstrates its genetic heterogeneity, and reassesses the nosological boundaries between MmD and RSMD.

Electrophysiological findings in X-linked myopathy with excessive autophagy.

We report electrophysiological features and magnetic resonance imaging muscle findings in 4 patients and 1 female carrier of X-linked myopathy with excessive autophagy. Motor units were polyphasic with high mean amplitude and normal duration. The thigh muscles were most severely involved, but myotonic discharges were abundant in both clinically affected and unaffected muscles. Along with the clinicopathological features, these electrophysiological findings distinguish X-linked myopathy with excessive autophagy from other limb-girdle myopathies.