Adult-onset Nemaline Myopathy Research Articles

CONGENITAL MYOPATHIES – NEMALINE MYOPATHIES: EP.39 Adult-onset nemaline myopathy due to a novel homozygous variant in the TNNT1 gene

CONGENITAL MYOPATHIES – NEMALINE MYOPATHIES: EP.39 Adult-onset nemaline myopathy due to a novel homozygous variant in the TNNT1 gene

Biallelic Mutations in MYPN, Encoding Myopalladin, Are Associated with Childhood-Onset, Slowly Progressive Nemaline Myopathy

Nemaline myopathy (NM) is a common form of congenital nondystrophic skeletal muscle disease characterized by muscular weakness of proximal dominance, hypotonia, and respiratory insufficiency but typically not cardiac dysfunction. Wide variation in severity has been reported. Intranuclear rod myopathy is a subtype of NM in which rod-like bodies are seen in the nucleus, and it often manifests as a severe phenotype. Although ten mutant genes are currently known to be associated with NM, only ACTA1 is associated with intranuclear rod myopathy. In addition, the genetic cause remains unclear in approximately 25%-30% of individuals with NM. We performed whole-exome sequencing on individuals with histologically confirmed but genetically unsolved NM. Our study included individuals with milder, later-onset NM and identified biallelic loss-of-function mutations in myopalladin (MYPN) in four families. Encoded MYPN is a sarcomeric protein exclusively localized in striated muscle in humans. Individuals with identified MYPN mutations in all four of these families have relatively mild, childhood- to adult-onset NM with slowly progressive muscle weakness. Walking difficulties were recognized around their forties. Decreased respiratory function, cardiac involvement, and intranuclear rods in biopsied muscle were observed in two individuals. MYPN was localized at the Z-line in control skeletal muscles but was absent from affected individuals. Homozygous knockin mice with a nonsense mutation in Mypn showed Z-streaming and nemaline-like bodies adjacent to a disorganized Z-line on electron microscopy, recapitulating the disease. Our results suggest that MYPN screening should be considered in individuals with mild NM, especially when cardiac problems or intranuclear rods are present.

Diagnosis of muscle diseases presenting with early respiratory failure.

Here we describe a clinical approach and differential diagnosis for chronic muscle diseases which include early respiratory failure as a prominent feature in their presentation (i.e. respiratory failure whilst still ambulant). These patients typically present to neurology or respiratory medicine out-patient clinics and a distinct differential diagnosis of neuromuscular aetiologies should be considered. Amyotrophic lateral sclerosis and myasthenia gravis are the important non-muscle diseases to consider, but once these have been excluded there remains a challenging differential diagnosis of muscle conditions, which will be the focus of this review. The key points in the diagnosis of these disorders are being aware of relevant symptoms, which are initially caused by nocturnal hypoventilation or diaphragmatic weakness; and identifying other features which direct further investigation. Important muscle diseases to identify, because their diagnosis has disease-specific management implications, include adult-onset Pompe disease, inflammatory myopathy, and sporadic adult-onset nemaline myopathy. Cases which are due to metabolic myopathy or muscular dystrophy are important to diagnose because of their implications for genetic counselling. Myopathy from sarcoidosis and colchicine each has a single reported case with this presentation, but should be considered because they are treatable. Disorders which have recently had their genetic aetiologies identified include hereditary myopathy with early respiratory failure (due to TTN mutations), the FHL1-related syndromes, and myofibrillar myopathy due to BAG3 mutation. Recently described syndromes include oculopharyngodistal muscular dystrophy that awaits genetic characterisation.

HEART's Original [症例] 心不全を契機に初めて診断された成人発症型ネマリンミオパチーの1症例

HEART's Original [症例] 心不全を契機に初めて診断された成人発症型ネマリンミオパチーの1症例

Adult nemaline myopathy with trabecular muscle fibers

The term "trabecular myopathy" has been used to designate a syndrome resembling limb-girdle muscular dystrophy in which the predominant pathological feature is an abundance of lobulated or trabecular muscle fibers. However, the validity of this nosological entity has not been verified. Herein we describe a 63-year-old man with a severe, progressive myopathy who exhibited the typical pathological features of both trabecular myopathy and nemaline myopathy in association with a biclonal gammopathy. In this case, adult-onset nemaline myopathy was probably the primary disease process. The diagnostic significance of trabecular muscle fibers remains uncertain.

Idiopathic adult‐onset nemaline myopathy presenting with isolated respiratory failure

Idiopathic adult-onset nemaline myopathy is a rare condition of unknown etiology that usually presents with proximal weakness. This case study reports a 60-year-old woman who presented with isolated type 2 respiratory failure secondary to bilateral hemidiaphragm weakness. A left vastus medialis muscle biopsy examined under light microscopy revealed appearances typical of nemaline myopathy. Electron microscopy confirmed the presence of nemaline rods in most muscle fibers, thus establishing idiopathic adult-onset nemaline myopathy as the cause of her respiratory failure. Our patient's presentation highlights the importance of considering neuromuscular weakness as a cause of respiratory failure. Unless appropriate tests are performed-including a muscle biopsy, if indicated-specific neuromuscular diseases are easily missed. This can lead to inappropriate counseling and treatment.

C.P.1.07 Exercise intolerance as a presentation of adult onset nemaline (rod) myopathy

C.P.1.07 Exercise intolerance as a presentation of adult onset nemaline (rod) myopathy

Nemaline myopathy revealed by respiratory failure in adults

Summary Most forms of myopathy may involve the respiratory muscles and progress to respiratory failure. However, the diagnosis of myopathy is seldom considered in an adult patient with no history of muscle disease and presenting with respiratory failure. Nemaline myopathy (NM) is a rare disorder characterized by symmetrical diffuse muscle weakness and rod-like nemaline bodies in muscle fibers. Respiratory muscle involvement is a major determinant of mortality in congenital NM, but is rare in late onset NM. Here, we report that acute or chronic respiratory failure may be caused by NM in subjects with no known history of muscle disease. Adult-onset NM was diagnosed in a 67-year-old woman with chronic respiratory insufficiency. Late onset childhood NM was revealed by respiratory failure in twin sisters aged 31. The diagnosis was established by muscle biopsy and electron microscopy (and mutations in the nebulin gene in the two sisters). Long-term clinical improvement was obtained with non-invasive ventilation (NIV) in the three patients. In conclusion, respiratory failure in an adult patient with no known history may correspond to NM with diaphragm involvement. Long-term outcome may be favorable with NIV.

Sporadic, Adult-Onset Nemaline Myopathy Presenting as Camptocormia (Bent-Spine Syndrome)

Sporadic, Adult-Onset Nemaline Myopathy Presenting as Camptocormia (Bent-Spine Syndrome)

Adult-Onset Nemaline Myopathy and Monoclonal Gammopathy

A 45-year-old man with severe proximal muscle weakness had findings diagnostic of adult-onset nemaline myopathy. He also had a monoclonal gammopathy. This is the fifth report of adult-onset nemaline myopathy in a patient with monoclonal gammopathy, suggesting that the occurrence of these entities may be more than a chance association. Myocyte-bound immunoglobulin or light chains were not detected and immunotherapy was not effective in this patient. Other causes of adult-onset nemaline myopathy were ruled out, including the most common mutations of sarcomeric thin filament genes.

Isolated dropped head due to adult-onset nemaline myopathy treated by posterior fusion

Neck extensor muscle weakness causing dropped head is most commonly associated with myasthenia gravis, ALS, and paraspinous myopathy.1–3 Less often, myotonic dystrophy, facioscapulohumeral muscular dystrophy, hypothyroidism, chronic inflammatory demyelinating polyneuropathy, polymyositis/dermatomyositis, and inclusion body myositis are associated with dropped head.1 We describe a patient with isolated dropped head and no limb weakness due to adult-onset nemaline myopathy that improved with a posterior cervical spinal fusion. A 72-year-old man presented with a 10-year history of a progressive head drop. He denied limb weakness, diplopia, or imbalance. There was no family history of neuromuscular disorders. His physical examination revealed isolated neck extensor weakness with normal limb muscle strength (figure, A). Deep tendon reflexes and sensation were normal. Creatine kinase, thyroid-stimulating hormone, and acetylcholine receptor antibodies were normal or negative. Cervical spine MRI demonstrated multilevel degenerative changes. Sensory and motor …

0250 Adult-onset nemaline myopathy with severe dropped head: Complex repetitive discharges on electromyography

0250 Adult-onset nemaline myopathy with severe dropped head: Complex repetitive discharges on electromyography

Nemaline myopathy: a clinical study of 143 cases.

We report 143 Australian and North American cases of primary nemaline myopathy. As classified by the European Neuromuscular Centre guidelines, 23 patients had severe congenital, 29 intermediate congenital, 66 typical congenital, 19 childhood-onset, and 6 adult-onset nemaline myopathy. Inheritance was autosomal recessive in 29 patients, autosomal dominant in 41, sporadic in 72, and indeterminate in 1. Twenty-two patients had skeletal muscle actin mutations and 4 had mutations in the alpha-tropomyosin(slow) gene. Obstetric complications occurred in 49 cases. Seventy-five patients had significant respiratory disease during the first year of life, and 79 had feeding difficulties. Atypical features in a minority of cases included arthrogryposis, central nervous system involvement, and congenital fractures. Progressive distal weakness developed in a minority of patients. Thirty patients died, the majority during the first 12 months of life. All deaths were due to respiratory insufficiency, which was frequently underrecognized in older patients. Arthrogryposis, neonatal respiratory failure, and failure to achieve early motor milestones were associated with early mortality. Morbidity from respiratory tract infections and feeding difficulties frequently diminished with increasing age. Aggressive early management is warranted in most cases of congenital nemaline myopathy.