Nemaline Bodies Research Articles

Damage to the orbicularis oculi muscle may impair the development of dermatochalasis

The purpose of this article is to investigate the changes that occur in the orbicularis oculi muscle (OOM) in patients with dermatochalasis. The OOM specimens from 26 patients were collected during upper eyelid blepharoplasty. Each specimen was divided into three parts, which were then examined using different techniques: formalin embedding for light microscopy, free freezing for histochemical examination, and fixation in 3% glutaraldehyde for electron microscopy. The severity of dermatochalasis was classified according to the anatomical landmarks. 78 specimens from patients with dermatochalasis were evaluated. Under light microscopy, specimens showed an increase in muscle fiber size variation, rounding of muscle fibers, and lobulation of myocytes in a fibrotic background. Under electron microscopy, loss of myofilaments, vacuolar vesicles, and swollen mitochondria were observed, along with osmophilic aggregates resembling nemadine bodies and collagen fibrils. A statistically significant association between the progression of dermatochalasis and the presence of aggregates resembling nemaline bodies was found (p- value < 0.005). Significant changes occur in the OOM in patients with dermatochalasis and the presence of aggregates resembling nemaline bodies is correlated with the degree of eyelid drooping. Thus, OOM may contribute in dermatochalasis progression.

Synaptopodin-2 Isoforms Have Specific Binding Partners and Display Distinct, Muscle Cell Type-Specific Expression Patterns.

Synaptopodin-2 (SYNPO2) is a protein associated with the Z-disc in striated muscle cells. It interacts with α-actinin and filamin C, playing a role in Z-disc maintenance under stress by chaperone-assisted selective autophagy (CASA). In smooth muscle cells, SYNPO2 is a component of dense bodies. Furthermore, it has been proposed to play a role in tumor cell proliferation and metastasis in many different kinds of cancers. Alternative transcription start sites and alternative splicing predict the expression of six putative SYNPO2 isoforms differing by extended amino- and/or carboxy-termini. Our analyses at mRNA and protein levels revealed differential expression of SYNPO2 isoforms in cardiac, skeletal and smooth muscle cells. We identified synemin, an intermediate filament protein, as a novel binding partner of the PDZ-domain in the amino-terminal extension of the isoforms mainly expressed in cardiac and smooth muscle cells, and demonstrated colocalization of SYNPO2 and synemin in both cell types. A carboxy-terminal extension, mainly expressed in smooth muscle cells, is sufficient for association with dense bodies and interacts with α-actinin. SYNPO2 therefore represents an additional and novel link between intermediate filaments and the Z-discs in cardiomyocytes and dense bodies in smooth muscle cells, respectively. In pathological skeletal muscle samples, we identified SYNPO2 in the central and intermediate zones of target fibers of patients with neurogenic muscular atrophy, and in nemaline bodies. Our findings help to understand distinct functions of individual SYNPO2 isoforms in different muscle tissues, but also in tumor pathology.

A recurrent ACTA1 amino acid change in mosaic form causes milder asymmetric myopathy

We describe three patients with asymmetric congenital myopathy without definite nemaline bodies and one patient with severe nemaline myopathy. In all four patients, the phenotype had been caused by pathogenic missense variants in ACTA1 leading to the same amino acid change, p.(Gly247Arg). The three patients with milder myopathy were mosaic for their variants. In contrast, in the severely affected patient, the missense variant was present in a de novo, constitutional form. The grade of mosaicism in the three mosaic patients ranged between 20 % and 40 %. We speculate that the milder clinical and histological manifestations of the same ACTA1 variant in the patients with mosaicism reflect the lower abundance of mutant actin in their muscle tissue. Similarly, the asymmetry of body growth and muscle weakness may be a consequence of the affected cells being unevenly distributed. The partial improvement in muscle strength with age in patients with mosaicism might be due to an increased proportion over time of nuclei carrying and expressing two normal alleles.

Actin Polymerization Defects Induce Mitochondrial Dysfunction in Cellular Models of Nemaline Myopathies.

Nemaline myopathy (NM) is one of the most common forms of congenital myopathy and it is identified by the presence of "nemaline bodies" (rods) in muscle fibers by histopathological examination. The most common forms of NM are caused by mutations in the Actin Alpha 1 (ACTA1) and Nebulin (NEB) genes. Clinical features include hypotonia and muscle weakness. Unfortunately, there is no curative treatment and the pathogenetic mechanisms remain unclear. In this manuscript, we examined the pathophysiological alterations in NM using dermal fibroblasts derived from patients with mutations in ACTA1 and NEB genes. Patients' fibroblasts were stained with rhodamine-phalloidin to analyze the polymerization of actin filaments by fluorescence microscopy. We found that patients' fibroblasts showed incorrect actin filament polymerization compared to control fibroblasts. Actin filament polymerization defects were associated with mitochondrial dysfunction. Furthermore, we identified two mitochondrial-boosting compounds, linoleic acid (LA) and L-carnitine (LCAR), that improved the formation of actin filaments in mutant fibroblasts and corrected mitochondrial bioenergetics. Our results indicate that cellular models can be useful to study the pathophysiological mechanisms involved in NM and to find new potential therapies. Furthermore, targeting mitochondrial dysfunction with LA and LCAR can revert the pathological alterations in NM cellular models.

Marked neuropsychiatric involvement and dysmorphic features in nemaline myopathy.

Inherited nemaline myopathy is one of the most common congenital myopathies. This genetically heterogeneous disease is defined by the presence of nemaline bodies in muscle biopsy. The phenotypic spectrum is wide and cognitive involvement has been reported, although not extensively evaluated. We report two nemaline myopathy patients presenting pronounced central nervous system involvement leading to functional compromise and novel facial and skeletal dysmorphic findings, possibly expanding the disease phenotype. One patient had two likely pathogenic NEB variants, c.2943G > A and c.8889 + 1G > A, and presented cognitive impairment and dysmorphic features, and the other had one pathogenic variant in ACTA1, c.169G > C (p.Gly57Arg), presenting autism spectrum disorder and corpus callosum atrophy. Both patients had severe cognitive involvement despite milder motor dysfunction. We raise the need for further studies regarding the role of thin filament proteins in the central nervous system and for a systematic cognitive assessment of congenital myopathy patients.

VP163 Filaminopathy presenting as myofibrillar myopathy with nemaline bodies and ring fibers

VP163 Filaminopathy presenting as myofibrillar myopathy with nemaline bodies and ring fibers

Clinico-pathological and gene features of 15 nemaline myopathy patients from a single Chinese neuromuscular center.

Nemaline myopathy, the most common of the congenital myopathies, is caused by various genetic mutations. In this study, we attempted to investigate the clinical features, muscle pathology and genetic features of 15 patients with nemaline myopathy. Among the 15 patients, there were 9 (60.00%) males and 6 (40.00%) females, and 9 (60.00%) of them came from three families respectively. The age of seeing a doctor ranged from 9 to 52years old, the age of onset was from 5 to 23years old, and the duration of disease ranged from 3 to 35years. Ten out of the 15 patients had high arched palate and elongated face. Only one patient had mild respiratory muscle involvement and none had dysphagia. Muscle biopsies were performed in 9 out of the 15 patients. Pathologically, muscle fibers of different sizes, atrophic muscle fibers and compensatory hypertrophic fibers could be found, and occasionally degenerated and necrotic muscle fibers were observed. Different degrees of nemaline bodies aggregation could be seen in all 9 patients. The distribution of type I and type II muscle fibers were significantly abnormal in patients with nemaline myopathy caused by NEB gene, however, it was basically normal in patients with nemaline myopathy caused by TPM3 gene and ACTA1 gene. Electron microscopic analysis of 6 patients showed that nemaline bodies aggregated between myofibrils were found in 5(83.33%) cases, and most of them were located near the Z band, but no intranuclear rods were found. The gene analysis of 15 NM patients showed that three NM-related genes were harbored, including 11 (73.33%) patients with NEB, 3 (20.00%) patients with TPM3, and 1 (6.67%) patient with ACTA1, respectively. A total of 12 mutation sites were identified and included 10 (83.33%) mutations in exon and 2(16.67%) mutations in intron. The clinical phenotype of nemaline myopathy is highly heterogeneous. Muscle pathology shows that nemaline bodies aggregation is an important feature for the diagnosis of NM. NEB is the most frequent causative gene in this cohort. The splicing mutation, c.21522 + 3A > G may be the hotspot mutation of the NEB gene in Chinese NM patients.

Observations of nemaline bodies in muscle biopsies of critically ill patients infected with SARS-CoV-2.

Patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who have been admitted to the intensive care unit (ICU) often face months of physical disability after discharge. To optimize recovery, it is important to understand the role of musculoskeletal alterations in critically ill patients infected with SARS-CoV-2. The main aim of the present study was to describe the presence and morphology of nemaline bodies found in the skeletal muscle tissue from critically ill patients infected with SARS-CoV-2. In n = 7 patients infected with SARS-CoV-2, ultrastructural characteristics of vastus lateralis muscle obtained on days 1-3 and days 5-8 following ICU admission were investigated in more detail with electron microscopy. Those muscle biopsies consistently showed variable degrees of myofiber necrosis and myofibrillar disorganization. In 4/7 (57%) patients on days 5-8, the Z-line material accumulated into nemaline bodies with a typical lattice-like appearance at higher magnification, similar to that found in nemaline myopathy. This study is the first to describe the disintegration of myofibrils and the accumulation of Z-line material into nemaline bodies in the skeletal muscle tissue obtained from critically ill coronavirus disease-19 patients following ICU admission, which should be interpreted primarily as a non-specific pathological response of extreme myofibrillar disintegration associated with myofiber necrosis.

A KLHL40 3' UTR splice-altering variant causes milder NEM8, an under-appreciated disease mechanism.

Nemaline myopathy 8 (NEM8) is typically a severe autosomal recessive disorder associated with variants in the kelch-like family member 40 gene (KLHL40). Common features include fetal akinesia, fractures, contractures, dysphagia, respiratory failure and neonatal death. Here, we describe a 26-year-old man with relatively mild NEM8. He presented with hypotonia and bilateral femur fractures at birth, later developing bilateral Achilles' contractures, scoliosis, and elbow and knee contractures. He had walking difficulties throughout childhood and became wheelchair bound from age 13 after prolonged immobilization. Muscle magnetic resonance imaging at age 13 indicated prominent fat replacement in his pelvic girdle, posterior compartments of thighs and vastus intermedius. Muscle biopsy revealed nemaline bodies and intranuclear rods. RNA sequencing and western blotting of patient skeletal muscle indicated significant reduction in KLHL40 mRNA and protein, respectively. Using gene panel screening, exome sequencing and RNA sequencing, we identified compound heterozygous variants in KLHL40; a truncating 10.9kb deletion in trans with a likely pathogenic variant (c.*152G > T) in the 3' untranslated region (UTR). Computational tools SpliceAI and Introme predicted the c.*152G > T variant created a cryptic donor splice site. RNA-seq and in vitro analyses indicated that the c.*152G > T variant induces multiple de novo splicing events that likely provoke nonsense mediated decay of KLHL40 mRNA explaining the loss of mRNA expression and protein abundance in the patient. Analysis of 3' UTR variants in ClinVar suggests variants that introduce aberrant 3' UTR splicing may be underrecognized in Mendelian disease. We encourage consideration of this mechanism during variant curation.

Немалиновая миопатия редкой формы (случай из практики)

Introduction Nemaline myopathies (NM) are a group of neuromuscular diseases, the distinctive histological feature of which are nemaline rods in myosymplasts. The purpose of this work is to describe the morphology of a rare form of primary nemaline myopathy that progresses in adulthood. Material and methods The surgical material of the paravertebral muscles of a 51-year-old patient with scoliotic deformity at the level of L4-S1, who was repeatedly operated on to correct spinal deformity due to neurological disorders, was studied. Paraffin sections were stained with hematoxylineosin, according to Masson, using the Ptah method, studied using a 3DHISTECH Pannoramic MIDI II BF scanning microscope to digitize preparations using Whole slide imaging technology in two modes: Single layer mode and Extended focus (3DHISTECH, Hungary). Results In the fragments of the altered muscle tissue, filamentous structures of nemaline bodies in myosymplasts were identified, which were located diffusely-dotted throughout the sarcoplasm or formed clusters of various configurations. There was an increased variability in the diameters of muscle fibers, internal nuclei, myosymplasts altered by contraction and with signs of myophagy, patterns of gradual replacement of muscle fibers by adipocytes, massive fatty degeneration of fibers, and fibrosis of the interstitial space. Intramuscular nerve trunks showed signs of complete involution; fibrous perineurium was preserved, and there were single nerve fibers; neuromuscular spindles were distinguished by an enlarged connective tissue capsule. The vessels of the arterial flow had signs of fibrosis and obliteration of the lumen; the vessels of the venous bed were tortuous. Discussion Due to a large number of genes responsible for NM, genetic search can be difficult and is effective only in 50 % of cases. It has been established that nemaline bodies can be distributed diffusely or form clusters of irregular shape, more often subsarcolemmal and characteristic of small fibers. In the presented clinical case, nemaline bodies were observed over the entire area of the fibers and were characteristic of myosymplasts of various sizes. Conclusion The histopathological study of the paravertebral muscles established the neuromuscular nature of the disease, being nemaline myopathy that progressed in adulthood and had not been diagnosed at previous stages of treatment.

O.03 Nemaline myopathy type 6: From pathology to therapeutics

Patients harboring variants in <i>KBTBD13</i> (NEM6) display impaired muscle relaxation, which compromises normal muscle function and daily-life activities. Histopathologically, NEM6 is characterized by the presence of myofibers containing nemaline bodies and a predominance of type I fibers. The majority of NEM6 patients harbor the Dutch founder mutation (c.1222C>T, p.Arg408Cys). Recently, we revealed that the R408C variantin <i>KBTBD13</i> slows muscle relaxation through an actin-based mechanism. To date, no therapy is available to treat NEM6. To fill this void, we developed a Kbtbd13^R408C knock-in mouse model. To identify a therapeutic window, we first performed a natural history study to characterize time of disease onset and progression in homozygous Kbtbd13^R408C knock-in at 1, 3, 9 and 18 months of age. Morphological and functional assays of soleus muscle showed that Kbtbd13^R408C knock-in mice closely recapitulate the human NEM6 phenotype: slow relaxation kinetics and muscle weakness was observed, in addition to the presence of nemaline bodies, type I fiber predominance, and hypertrophy of type I and IIa myofibers. This phenotype was absent at 1 month, developed between 1-3 months, and showed little progression after 9 months of age. Our treatment of choice was the knock-down of mutant <i>Kbtbd13</i> transcript. This choice was based on experiments on homozygous Kbtbd13-KO mice, which showed no overt phenotype at 3 and 9 months of age. Thus, Kbtbd13-deficiency is well tolerated. We treated soleus with a single intramuscular injection with an AAV9 containing a short-hairpin RNA for Kbtbd13 (AAV9-shKbtbd13). We hypothesized that a reduction in mutant transcript level would prevent or reverse disease development. Our data demonstrate that a single injection knocked down mutant <i>Kbtbd13</i> transcript levels by >90% in 3 (injected at 1-month, prior to disease development) and 9 month (injected at 7-months, at which an overt disease phenotype was present) old mice. Importantly, in treated mice, the relaxation kinetics were normalized to those of wild-type mice. Additionally, in treated mice, we observed a >70% reduction in the number of nemaline rod positive fibers. In conclusion, our results show the natural history of NEM6 in a novel mouse model and the promise of knocking down mutant transcript to prevent and reverse the NEM6 phenotype.

P.02 Mild nemaline myopathy 10 caused by a novel missense homozygous mutation in LMOD3: broadening the phenotype-genotype correlation

Nemaline myopathy (NM) is a heterogeneous group of conditions characterized by the presence of muscle weakness and the accumulation of nemaline bodies in the muscle biopsy. So far, mutations in 14 genes have been related to both recessive and dominant forms of NM. <i>LMOD3</i> encodes for the Leimodin-3 protein, which is expressed in the skeletal and cardiac muscle. The majority of described mutations in <i>LMOD3</i> are truncating mutations and cause a severe autosomal recessive congenital myopathy (NEM-10), characterized by early-onset hypotonia, generalized muscle weakness and respiratory insufficiency. Most of the patients also present polyhydramnios, reduced fetal movements, arthrogryposis or frequent contractures, and they usually die during early childhood. Here we describe a family with two affected adult sisters with a novel homozygous missense mutation in LMOD3 presenting a very mild phenotype, providing further evidence to the phenotype-genotype correlation of NEM-10. The proband, a 54-year-old woman was the first child of healthy consanguineous parents. She presented with mild hypotonia at birth and delayed motor milestones. She was never able to run, and presented frequent falls during infancy. Examination revealed high arched palate, bilateral facial weakness, and mild weakness involving neck flexors, iliopsoas and knee flexors. Her sister had the same phenotype. Serum CK were within normal levels. A muscle biopsy taken from the triceps brachii revealed mild variation in the fiber size, and very rare fibres containing nemaline bodies. Both affected sisters presented a novel homozygous missense c.1030C>T, p.Arg344Trp (NM_198271.4) mutation identified in the <i>LMOD3</i> gene through a NGS custom gene panel analyzing 139 neuromuscular-related genes. Our work broadens the mutational spectrum of <i>LMOD3</i> gene and contributes to better understand the clinical heterogeneity of nemaline myopathy.

P.01 A KLHL40 3′UTR splice-altering variant causes milder NEM8

Nemaline myopathy 8 (NEM8) is typically a severe autosomal recessive disorder associated with variants in the kelch-like family member 40 gene (KLHL40). To date, only protein-altering pathogenic variants in <i>KLHL40</i> have been implicated in NEM8. Common features include fetal akinesia/hypokinesia, fractures, contractures, dysphagia, respiratory failure, and neonatal death. Here, we describe a 26-year-old man with relatively mild NEM8. He presented with hypotonia and bilateral femur fractures at birth, later developing bilateral Achilles' contractures, scoliosis, and elbow and knee contractures. He had walking difficulties throughout his childhood and became wheelchair bound from age 13 after prolonged immobilization. Muscle MRI at age 13 indicated prominent fat replacement in his pelvic girdle, posterior compartments of thighs, vastus intermedius and legs. Muscle biopsy revealed nemaline bodies and intranuclear rods. RNA sequencing and western blotting of patient skeletal muscle indicated significant reduction in <i>KLHL40</i> mRNA and protein respectively. Using gene panel screening, exome sequencing and RNA sequencing, we identified compound heterozygous variants in <i>KLHL40</i>; a truncating 10.9 kb deletion in trans with a likely pathogenic variant (c.*152G>T) in the 3' untranslated region (UTR). Computational tools SpliceAI and Introme predicted the c.*152G>T variant created a cryptic donor splice site. RNA sequencing and in vitro analyses indicated that the c.*152G>T variant induces multiple de novo splicing events. Nonsense mediated decay of <i>KLHL40</i> mRNA, provoked by introduction of 3' UTR introns, likely explains the loss of both mRNA and protein expression in the patient. Our analysis of 3' UTR variants in ClinVar suggests that SNPs that introduce aberrant 3'UTR splicing may be under recognised in Mendelian disease. We encourage consideration of this mechanism during disease gene screening.

Generation of two isogenic induced pluripotent stem cell lines from a 1-month-old nemaline myopathy patient harbouring a homozygous recessive c.121C > T (p.Arg39Ter) variant in the ACTA1 gene

Nemaline myopathy (NM) is a congenital skeletal muscle disorder that typically results in muscle weakness and the presence of rod-like structures (nemaline bodies) in the sarcoplasma and/or in the nuclei of myofibres. Two induced pluripotent stem cell (iPSC) lines were generated from the lymphoblastoid cells of a 1-month-old male with severe NM caused by a homozygous recessive mutation in the ACTA1 gene (c.121C > T, p.Arg39Ter). The iPSC lines demonstrated typical morphology, expressed pluripotency markers, exhibited trilineage differentiation potential and displayed a normal karyotype. These isogenic lines represent a potential resource to investigate and model recessive ACTA1 disease in a human context.

Clinicopathologic Profiles of Sporadic Late-Onset Nemaline Myopathy: Practical Importance of Anti-α-Actinin Immunostaining.

Background and ObjectivesSporadic late-onset nemaline myopathy (SLONM) is a treatable or otherwise fatal myopathy. Diagnosis of SLONM is still challenging, and no therapeutic consensus has been achieved. Here, we reported the clinicopathologic features and long-term follow-up data of SLONM in a Chinese cohort.MethodsWe performed a retrospective evaluation of clinical, pathologic, and treatment outcomes of 17 patients with SLONM diagnosed between March 1986 and April 2021 at our neuromuscular center. Immunohistochemistry (IHC) with antibodies against 5 Z-disc–associated proteins was performed in the muscle biopsies of SLONM to identify a potential pathologic marker in aid of diagnosis. In comparison, we also performed muscle IHC in patients with selective type II fiber atrophy (n = 22), neurogenic atrophy (n = 22), mitochondrial myopathy (n = 5), immune-mediated necrotizing myopathy (n = 5), and normal controls (n = 5).ResultsMost of the patients exhibited asymmetric limb muscles weakness (71%, 12/17) and neck extensor weakness (53%, 9/17). Immunofixation electrophoresis was performed in 11 patients, and 4 of them were identified with monoclonal gammopathy of undetermined significance (MGUS). EMG from 16 patients demonstrated a myopathic pattern with spontaneous activities in 69% (11/16) of them. Muscle MRI showed preferential involvement of paraspinal, gluteus minimus and medius, semimembranosus, and soleus muscles. Suspected nemaline bodies on modified Gomori trichrome were confirmed by IHC using anti–α-actinin antibody (100%, 17/17), anti-myotilin antibody (94%, 16/17), anti-desmin antibody (94%, 16/17), anti–α-B crystallin antibody (65%, 11/17), and anti-telethonin antibody (18%, 3/17) with various positive rates. Notably, anti–α-actinin IHC showed the highest percentage of strongly positive staining (77%, 13/17), being the only one without negative results. Moderate improvement following autologous stem cell transplantation (ASCT) was noted in 3/4 patients with MGUS; favorable outcomes were also achieved in 6/7 patients without MGUS, including 3 patients with complete recovery who were given a combined treatment of prednisone and another immunosuppressant.DiscussionSLONM is a treatable myopathy with ASCT or traditional immunotherapy, especially when combined with steroids and immunosuppressants. Anti–α-actinin immunostaining is the most reliable pathologic marker to identify rod-bearing fibers, and it should be performed routinely in adult patients with undiagnosed nonnecrotic myopathies.

68-year old man with progressive weakness and ventilator dependent respiratory failure: a case report of sporadic late onset nemaline myopathy

BackgroundNeuromuscular pathologies must be considered when caring for patients with persistent or progressive respiratory failure. Pertinent disease states may involve skeletal muscles of respiration or associated neurologic structures including motor neurons, peripheral neurons and the neuromuscular junction. Diagnosis may require pulmonary function testing, neurophysiologic studies, imaging, and/or muscle biopsy.Case presentationA 68-year-old male was transferred to our intensive care unit (ICU) for management of ventilator dependent respiratory failure. Upon further historical review, he described gradually worsening gait instability and muscle weakness, which was previously attributed to vascular Parkinsonism in the setting of known cerebrovascular disease. Upon arrival to our hospital, he was found to have elevated muscle specific enzymes, prompting evaluation for neuromuscular causes of respiratory failure. He was also found to have elevated HMG-CoA Reductase (HMGCR) antibodies. Ultimately, a right quadriceps muscle biopsy was performed and electron microscopy identified nemaline bodies within skeletal myofibers. Given the clinical course and other histopathologic findings, he was diagnosed with Sporadic late-onset nemaline myopathy (SLONM).ConclusionThe diagnosis of neuromuscular disease in patients with ventilator dependent respiratory failure is challenging. A detailed history of a patient’s clinical course prior to hospitalization is key and may raise suspicion for underlying neuromuscular pathology. Further evaluation in non-critically ill patients may include pulmonary function, electromyography and confirmatory muscle biopsy. Sporadic late onset nemaline myopathy remains a rare disease entity which rarely presents with respiratory failure and lacks effective treatment.

Troponin-T type 1 (TNNT1)-related nemaline myopathy: unique respiratory phenotype and muscle pathology findings

Biallelic pathogenic variants in the troponin T type 1 (TNNT1) gene cause a severe form of congenital nemaline myopathy. Typical features include severe motor delay, proximal contractures and weakness, pectus carinatum, chest wall rigidity and tremor. If left untreated, respiratory failure leads to early death at a median age of 18 months. Here we report on three non-Amish, unrelated patients harbouring novel TNNT1 variants. The peculiar combination of respiratory muscle weakness and chest wall stiffness caused early severe hypoventilation warranting the use of high pressures on BiPAP ventilator, with subsequent rapid escalation of pressures delivered with limited efficacy secondary to the extreme rib cage stiffness. Severe respiratory impairment occurred despite a relatively milder motor involvement in one patient. Muscle biopsies from two individuals showed predominant involvement of type 1 fibres, abundant nemaline bodies, marked fibrosis and loss of TNNT1 protein. We aim to increase the awareness of the challenges of managing respiratory support in patients with this unique respiratory phenotype.

Generation of two isogenic induced pluripotent stem cell lines from a 10-year-old typical nemaline myopathy patient with a heterozygous dominant c.541G>A (p.Asp179Asn) pathogenic variant in the ACTA1 gene

Nemaline myopathy (NM) is a congenital myopathy typically characterized by skeletal muscle weakness and the presence of nemaline bodies in myofibres. Approximately 25% of NM cases are caused by variants in ACTA1. We generated two induced pluripotent stem cell lines from lymphoblastoid cells of a 10-year-old female with typical NM harbouring a dominant pathogenic variant in ACTA1 (c.541C>A). The isogenic lines displayed typical iPSC morphology, expressed pluripotency markers, and could differentiate into each of the three germ layers. Although the lines have partial or complete X chromosome duplication, they may still prove useful as models of human ACTA1 disease.

Inflammatory features in sporadic late-onset nemaline myopathy are independent from monoclonal gammopathy.

ABSTRACTSporadic late‐onset nemaline myopathy (SLONM) is a rare adult‐onset non‐hereditary disease with subacute proximal muscle and often axial muscle weakness, characterized by the presence of nemaline bodies in skeletal muscle biopsies. Considering its association with concurrent monoclonal gammopathy of undetermined significance (MGUS), the disease is classified into two major subtypes (1) SLONM without MGUS (SLONM‐noMGUS) and (2) with MGUS (SLONM‐MGUS) association. SLONM associated with HIV infection (SLONM‐HIV) is also reported. SLONM‐MGUS has been shown to be associated with poorer prognosis and required aggressive treatment including high‐dose melphalan and autologous stem cell transplantation. The approach is currently debatable as recent reports suggested effectiveness of intravenous immunoglobulin as initial treatment with indifference of overall survival despite the presence of MGUS. Our study aimed to find an underlying basis by review of pathological features in 49 muscle biopsy proven‐SLONM from two large tertiary centers in Japan and Germany (n = 49: SLONM‐noMGUS = 34, SLONM‐MGUS = 13, SLONM‐HIV = 2). We compared pathological findings in SLONM‐noMGUS and SLONM‐MGUS and focused on the presence of any detectable inflammatory features by immunohistochemistry. The clinical and histological features in SLONM‐noMGUS and SLONM‐MGUS were not distinctively different except for more common regenerating fibers (>5% of myofibers) present in SLONM‐MGUS (p < 0.01). HLA‐ABC expression and fine granular p62 were observed in 66.7% and 78.3% of SLONM, respectively. The predominant inflammatory cells were CD68+ cells. The inflammatory cells showed positive correlations with the percentage of nemaline‐containing fibers (p < 0.001). In conclusion, inflammatory features are present although rather mild in SLONM. This finding contributes to the hypothesis of an acquired inflammatory disease pathogenesis and opens the possibility to offer immunotherapy in SLONM with inflammatory features regardless of the monoclonal gammopathy status.

Clinico-pathological features and mutational spectrum of 16 nemaline myopathy patients from a Chinese neuromuscular center

Nemaline myopathy (NM) is a congenital myopathy of great heterogeneity, characterized by the presence of rods in the cytoplasm of muscle fibers. The samples of 16 nemaline myopathy patients diagnosed by characteristically pathological features went through whole exon sequencing. Clinico-pathological and genetic features of the cases were systematically analyzed. According to the classification of nemaline myopathy by ENMC, 8 cases are typical congenital subtype, 6 cases are childhood/juvenile onset subtype and 2 case are adult onset subtype. In histological findings, characteristic purple-colored rods are discovered under modified gömöri trichrome staining (MGT). Electron microscopy revealed the presence of high electron-dense nemaline bodies around the submucosa and the nucleus nine patients (9/16 56.3%) were detected pathogenic causative mutations, among whom mutations in the NEB gene were the most frequent (6 patients, 66.7%). KBTBD13 gene mutation was discovered in two patients and ACTA1 gene mutation was discovered in 1 patient. Nemaline myopathy is a congenital myopathy with highly clinico-pathological and genetic heterogeneity. NEB gene mutation is the most common mutation, in which splicing change c.21522 +3A > G is hotspot mutation in Chinese NM patients.