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EMG: myopathic abnormalities

MedGen UID:
867362
Concept ID:
C4021726
Pathologic Function
Synonyms: EMG: myopathic changes; EMG: myopathy; Myopathic electromyogram
 
HPO: HP:0003458

Definition

The presence of abnormal electromyographic patterns indicative of myopathy, such as small-short polyphasic motor unit potentials. [from HPO]

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
  • EMG: myopathic abnormalities

Conditions with this feature

Elevated circulating creatine kinase concentration
MedGen UID:
69128
Concept ID:
C0241005
Finding
An elevation of the level of the enzyme creatine kinase (also known as creatine phosphokinase (CK; EC 2.7.3.2) in the blood. CK levels can be elevated in a number of clinical disorders such as myocardial infarction, rhabdomyolysis, and muscular dystrophy.
Sarcotubular myopathy
MedGen UID:
78750
Concept ID:
C0270968
Congenital Abnormality
A mild subtype of autosomal recessive limb girdle muscular dystrophy characterized by slowly progressive proximal muscle weakness and wasting of the pelvic and shoulder girdles with onset that usually occurs during the second or third decade of life. Clinical presentation is variable and can include calf psuedohypertrophy, joint contractures, scapular winging, muscle cramping and/or facial and respiratory muscle involvement.
Myopathy, centronuclear, 2
MedGen UID:
98049
Concept ID:
C0410204
Disease or Syndrome
Centronuclear myopathy is a condition characterized by muscle weakness (myopathy) and wasting (atrophy) in the skeletal muscles, which are the muscles used for movement. The severity of centronuclear myopathy varies among affected individuals, even among members of the same family.\n\nPeople with centronuclear myopathy begin experiencing muscle weakness at any time from birth to early adulthood. The muscle weakness slowly worsens over time and can lead to delayed development of motor skills, such as crawling or walking; muscle pain during exercise; and difficulty walking. Some affected individuals may need wheelchair assistance as the muscles atrophy and weakness becomes more severe. In rare instances, the muscle weakness improves over time.\n\nSome people with centronuclear myopathy experience mild to severe breathing problems related to the weakness of muscles needed for breathing. People with centronuclear myopathy may have droopy eyelids (ptosis) and weakness in other facial muscles, including the muscles that control eye movement. People with this condition may also have foot abnormalities, a high arch in the roof of the mouth (high-arched palate), and abnormal side-to-side curvature of the spine (scoliosis). Rarely, individuals with centronuclear myopathy have a weakened heart muscle (cardiomyopathy), disturbances in nerve function (neuropathy), or intellectual disability.\n\nA key feature of centronuclear myopathy is the displacement of the nucleus in muscle cells, which can be viewed under a microscope. Normally the nucleus is found at the edges of the rod-shaped muscle cells, but in people with centronuclear myopathy the nucleus is located in the center of these cells. How the change in location of the nucleus affects muscle cell function is unknown.
Danon disease
MedGen UID:
209235
Concept ID:
C0878677
Disease or Syndrome
Danon disease is a multisystem condition with predominant involvement of the heart, skeletal muscles, and retina, with overlying cognitive dysfunction. Males are typically more severely affected than females. Males usually present with childhood onset concentric hypertrophic cardiomyopathy that is progressive and often requires heart transplantation. Rarely, hypertrophic cardiomyopathy can evolve to resemble dilated cardiomyopathy. Most affected males also have cardiac conduction abnormalities. Skeletal muscle weakness may lead to delayed acquisition of motor milestones. Learning disability and intellectual disability, most often in the mild range, are common. Additionally, affected males can develop retinopathy with subsequent visual impairment. The clinical features in females are broader and more variable. Females are more likely to have dilated cardiomyopathy, with a smaller proportion requiring heart transplantation compared to affected males. Cardiac conduction abnormalities, skeletal muscle weakness, mild cognitive impairment, and pigmentary retinopathy are variably seen in affected females.
Desmin-related myofibrillar myopathy
MedGen UID:
330449
Concept ID:
C1832370
Disease or Syndrome
Myofibrillar myopathy (MFM) is a noncommittal term that refers to a group of morphologically homogeneous, but genetically heterogeneous chronic neuromuscular disorders. The morphologic changes in skeletal muscle in MFM result from disintegration of the sarcomeric Z disc and the myofibrils, followed by abnormal ectopic accumulation of multiple proteins involved in the structure of the Z disc, including desmin, alpha-B-crystallin (CRYAB; 123590), dystrophin (300377), and myotilin (TTID; 604103). Genetic Heterogeneity of Myofibrillar Myopathy Other forms of MFM include MFM2 (608810), caused by mutation in the CRYAB gene (123590); MFM3 (609200) (182920), caused by mutation in the MYOT gene (604103); MFM4 (609452), caused by mutation in the ZASP gene (LDB3; 605906); MFM5 (609524), caused by mutation in the FLNC gene (102565); MFM6 (612954), caused by mutation in the BAG3 gene (603883); MFM7 (617114), caused by mutation in the KY gene (605739); MFM8 (617258), caused by mutation in the PYROXD1 gene (617220); MFM9 (603689), caused by mutation in the TTN gene (188840); MFM10 (619040), caused by mutation in the SVIL UNC45B gene (611220); MFM11 (619178), caused by mutation in the UNC45B gene (611220); and MFM12 (619424), caused by mutation in the MYL2 gene (160781). 'Desmin-related myopathy' is another term referring to MFM in which there are intrasarcoplasmic aggregates of desmin, usually in addition to other sarcomeric proteins. Rigid spine syndrome (602771), caused by mutation in the SEPN1 gene (606210), is another desmin-related myopathy. Goebel (1995) provided a review of desmin-related myopathy.
Muscular dystrophy, congenital, with severe central nervous system atrophy and absence of large myelinated fibers
MedGen UID:
331338
Concept ID:
C1832665
Disease or Syndrome
Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 1
MedGen UID:
371919
Concept ID:
C1834846
Disease or Syndrome
POLG-related disorders comprise a continuum of overlapping phenotypes that were clinically defined long before their molecular basis was known. Most affected individuals have some, but not all, of the features of a given phenotype; nonetheless, the following nomenclature can assist the clinician in diagnosis and management. Onset of the POLG-related disorders ranges from infancy to late adulthood. Alpers-Huttenlocher syndrome (AHS), one of the most severe phenotypes, is characterized by childhood-onset progressive and ultimately severe encephalopathy with intractable epilepsy and hepatic failure. Childhood myocerebrohepatopathy spectrum (MCHS) presents between the first few months of life and about age three years with developmental delay or dementia, lactic acidosis, and a myopathy with failure to thrive. Other findings can include liver failure, renal tubular acidosis, pancreatitis, cyclic vomiting, and hearing loss. Myoclonic epilepsy myopathy sensory ataxia (MEMSA) now describes the spectrum of disorders with epilepsy, myopathy, and ataxia without ophthalmoplegia. MEMSA now includes the disorders previously described as spinocerebellar ataxia with epilepsy (SCAE). The ataxia neuropathy spectrum (ANS) includes the phenotypes previously referred to as mitochondrial recessive ataxia syndrome (MIRAS) and sensory ataxia neuropathy dysarthria and ophthalmoplegia (SANDO). About 90% of persons in the ANS have ataxia and neuropathy as core features. Approximately two thirds develop seizures and almost one half develop ophthalmoplegia; clinical myopathy is rare. Autosomal recessive progressive external ophthalmoplegia (arPEO) is characterized by progressive weakness of the extraocular eye muscles resulting in ptosis and ophthalmoparesis (or paresis of the extraocular muscles) without associated systemic involvement; however, caution is advised because many individuals with apparently isolated arPEO at the onset develop other manifestations of POLG-related disorders over years or decades. Of note, in the ANS spectrum the neuropathy commonly precedes the onset of PEO by years to decades. Autosomal dominant progressive external ophthalmoplegia (adPEO) typically includes a generalized myopathy and often variable degrees of sensorineural hearing loss, axonal neuropathy, ataxia, depression, parkinsonism, hypogonadism, and cataracts (in what has been called "chronic progressive external ophthalmoplegia plus," or "CPEO+").
Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 3
MedGen UID:
373087
Concept ID:
C1836439
Disease or Syndrome
Progressive external ophthalmoplegia is characterized by multiple mitochondrial DNA deletions in skeletal muscle. The most common clinical features include adult onset of weakness of the external eye muscles and exercise intolerance. Patients with C10ORF2-linked adPEO may have other clinical features including proximal muscle weakness, ataxia, peripheral neuropathy, cardiomyopathy, cataracts, depression, and endocrine abnormalities (summary by Fratter et al., 2010). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal dominant progressive external ophthalmoplegia, see PEOA1 (157640). PEO caused by mutations in the POLG gene (174763) are associated with more complicated phenotypes than those forms caused by mutations in the SLC25A4 (103220) or C10ORF2 genes (Lamantea et al., 2002).
Nemaline myopathy 1
MedGen UID:
373089
Concept ID:
C1836448
Disease or Syndrome
Nemaline myopathy-1 is a disorder characterized by muscle weakness, usually beginning in early childhood. The severity and pattern of muscle weakness varies, but most affected individuals show mildly delayed motor development, hypotonia, generalized muscle weakness, and weakness of the proximal limb muscles and neck muscles, resulting in difficulty running and easy fatigability. Most patients have respiratory insufficiency due to muscle weakness. Other common features include myopathic facies, high-arched palate, and scoliosis. Histologic findings on skeletal muscle biopsy are variable, even in patients with the same mutation. Muscle fibers can contain nemaline rod inclusions, or so-called subsarcolemmal 'cap' structures, as well as show overall fiber-type disproportion. It has been suggested that unknown modifying factors confer a tendency to one or another pattern of inclusions on skeletal muscle biopsy in those with TPM3 mutations (summary by Waddell et al., 2010 and Malfatti et al., 2013). For a discussion of genetic heterogeneity of nemaline myopathy, see 161800.
Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal dominant 2
MedGen UID:
322925
Concept ID:
C1836460
Disease or Syndrome
Progressive external ophthalmoplegia is characterized by multiple mitochondrial DNA deletions in skeletal muscle. The most common clinical features include adult onset of weakness of the external eye muscles and exercise intolerance. Both autosomal dominant and autosomal recessive inheritance can occur; autosomal recessive inheritance is usually more severe (Filosto et al., 2003; Luoma et al., 2004). PEO caused by mutations in the POLG gene are associated with more complicated phenotypes than those forms caused by mutations in the ANT1 or C10ORF2 genes (Lamantea et al., 2002). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal dominant progressive external ophthalmoplegia, see PEOA1 (157640).
Muscular dystrophy-dystroglycanopathy type B6
MedGen UID:
373284
Concept ID:
C1837229
Disease or Syndrome
MDDGB6 is an autosomal recessive congenital muscular dystrophy with impaired intellectual development and structural brain abnormalities (Longman et al., 2003). It is part of a group of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (Mercuri et al., 2009). For a discussion of genetic heterogeneity of congenital muscular dystrophy-dystroglycanopathy type B, see MDDGB1 (613155).
Myofibrillar myopathy 2
MedGen UID:
324735
Concept ID:
C1837317
Disease or Syndrome
Alpha-B crystallin-related myofibrillar myopathy is an autosomal dominant muscular disorder characterized by adult onset of progressive muscle weakness affecting both the proximal and distal muscles and associated with respiratory insufficiency, cardiomyopathy, and cataracts. There is phenotypic variability both within and between families (Fardeau et al., 1978; Selcen and Engel, 2003). A homozygous founder mutation in the CRYAB gene has been identified in Canadian aboriginal infants of Cree origin who have a severe fatal infantile hypertonic form of myofibrillar myopathy; see 613869. For a phenotypic description and a discussion of genetic heterogeneity of myofibrillar myopathy, see MFM1 (601419).
Autosomal recessive limb-girdle muscular dystrophy type 2J
MedGen UID:
324741
Concept ID:
C1837342
Disease or Syndrome
A form of limb-girdle muscular dystrophy that usually has a childhood onset (but can range from the first to third decade of life) of severe progressive proximal weakness, eventually involving the distal muscles. Some patients may remain ambulatory but most are wheelchair dependant 20 years after onset.
Tibial muscular dystrophy
MedGen UID:
333047
Concept ID:
C1838244
Disease or Syndrome
Udd distal myopathy – tibial muscular dystrophy (UDM-TMD) is characterized by weakness of ankle dorsiflexion and inability to walk on the heels after age 30 years. Disease progression is slow and muscle weakness remains confined to the anterior compartment muscles for many years. The long toe extensors become clinically involved after ten to 20 years, leading to foot drop and clumsiness when walking. In the mildest form, UDM-TMD can remain unnoticed even in the elderly. EMG shows profound myopathic changes in the anterior tibial muscle, but preservation of the extensor brevis muscle. Muscle MRI shows selective fatty degeneration of the anterior tibial muscles and other anterior compartment muscles of the lower legs. Serum CK concentration may be normal or slightly elevated. Muscle biopsy shows progressive dystrophic changes in the tibialis anterior muscle with rimmed vacuoles at the early stages and replacement with adipose tissue at later stages of the disease.
Myopathy and diabetes mellitus
MedGen UID:
333236
Concept ID:
C1839028
Disease or Syndrome
A rare, genetic, mitochondrial DNA-related mitochondrial myopathy disorder characterized by slowly progressive muscular weakness (proximal greater than distal), predominantly involving the facial muscles and scapular girdle, associated with insulin-dependent diabetes mellitus. Neurological involvement and congenital myopathy may be variably observed.
Autosomal dominant limb-girdle muscular dystrophy type 1F
MedGen UID:
333983
Concept ID:
C1842062
Disease or Syndrome
Autosomal dominant limb-girdle muscular dystrophy-2 is a myopathy characterized by proximal muscle weakness primarily affecting the lower limbs, but also affecting the upper limbs in most patients. Affected individuals also have distal muscle weakness of the hands and lower leg muscles. There is variability in presentation and progression. Some patients present in early childhood with mildly delayed walking and difficulty running and jumping, whereas others present as adults with mainly pelvic-girdle weakness. Patients with early onset tend to have a more severe disorder, and may develop contractures, loss of independent ambulation, and respiratory insufficiency. Muscle biopsy shows dystrophic changes with abnormal nuclei, rimmed vacuoles, and filamentous inclusions (summary by Melia et al., 2013). For a phenotypic description and a discussion of genetic heterogeneity of autosomal dominant limb-girdle muscular dystrophy, see LGMDD1 (603511).
Myosin storage myopathy
MedGen UID:
374868
Concept ID:
C1842160
Disease or Syndrome
Myosin storage myopathy, also known as hyaline body myopathy, is a congenital myopathy characterized by the accumulation of ATPase and antibody positive myosin in hyaline subsarcolemmal bodies in type I muscle fibers. The clinical features are variable, with different patients displaying proximal, scapuloperoneal, or generalized weakness and progressive or nonprogressive courses (summary by Dye et al., 2006).
Muscular dystrophy-dystroglycanopathy type B5
MedGen UID:
335764
Concept ID:
C1847759
Disease or Syndrome
MDDGB5 is an autosomal recessive congenital muscular dystrophy with impaired intellectual development and structural brain abnormalities (Brockington et al., 2001). It is part of a group of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (Mercuri et al., 2006). For a discussion of genetic heterogeneity of congenital muscular dystrophy-dystroglycanopathy type B, see MDDGB1 (613155).
Nemaline myopathy 2
MedGen UID:
342534
Concept ID:
C1850569
Disease or Syndrome
Nemaline myopathy-2 (NEM2) is an autosomal recessive skeletal muscle disorder with a wide range of severity. The most common clinical presentation is early-onset (in infancy or childhood) muscle weakness predominantly affecting proximal limb muscles. Muscle biopsy shows accumulation of Z-disc and thin filament proteins into aggregates named 'nemaline bodies' or 'nemaline rods,' usually accompanied by disorganization of the muscle Z discs. The clinical and histologic spectrum of entities caused by variants in the NEB gene is a continuum, ranging in severity. The distribution of weakness can vary from generalized muscle weakness, more pronounced in proximal limb muscles, to distal-only involvement, although neck flexor weakness appears to be rather consistent. Histologic patterns range from a severe usually nondystrophic disturbance of the myofibrillar pattern to an almost normal pattern, with or without nemaline bodies, sometimes combined with cores (summary by Lehtokari et al., 2014). For a discussion of genetic heterogeneity of nemaline myopathy, see NEM3 (161800). Mutations in the NEB gene are the most common cause of nemaline myopathy (Lehtokari et al., 2006).
Myopathy, myosin storage, autosomal recessive
MedGen UID:
340603
Concept ID:
C1850709
Disease or Syndrome
Autosomal recessive limb-girdle muscular dystrophy type 2B
MedGen UID:
338149
Concept ID:
C1850889
Disease or Syndrome
Dysferlinopathy includes a spectrum of muscle disease characterized by two major phenotypes: Miyoshi muscular dystrophy (MMD) and limb-girdle muscular dystrophy type 2B (LGMD2B); and two minor phenotypes: asymptomatic hyperCKemia and distal myopathy with anterior tibial onset (DMAT). MMD (median age of onset 19 years) is characterized by muscle weakness and atrophy, most marked in the distal parts of the legs, especially the gastrocnemius and soleus muscles. Over a period of years, the weakness and atrophy spread to the thighs and gluteal muscles. The forearms may become mildly atrophic with decrease in grip strength; the small muscles of the hands are spared. LGMD2B is characterized by early weakness and atrophy of the pelvic and shoulder girdle muscles in adolescence or young adulthood, with slow progression. Other phenotypes in this spectrum are scapuloperoneal syndrome and congenital muscular dystrophy. Asymptomatic hyperCKemia is characterized by marked elevation of serum CK concentration only. DMAT is characterized by early and predominant distal muscle weakness, particularly of the muscles of the anterior compartment of the legs.
GNE myopathy
MedGen UID:
381298
Concept ID:
C1853926
Disease or Syndrome
GNE myopathy is a slowly progressive muscle disease that typically presents between age 20 and 40 years with bilateral foot drop caused by anterior tibialis weakness. Lower-extremity muscle involvement progresses from the anterior to the posterior compartment of the lower leg, followed by hamstrings, then hip girdle muscles, with relative sparing of the quadriceps. A wheelchair may be needed about ten to 20 years after the onset of manifestations. The upper extremities, which may be affected within five to ten years of disease onset, do not necessarily follow a distal-to-proximal progression. In advanced stages, neck and core muscles can become affected.
Finnish upper limb-onset distal myopathy
MedGen UID:
400595
Concept ID:
C1864706
Disease or Syndrome
Finnish upper limb-onset distal myopathy is a rare, genetic distal myopathy characterized by slowly progressive distal to proximal limb muscle weakness and atrophy, with characteristic early involvement of thenar and hypothenar muscles. Patients present with clumsiness of the hands and stumbling in the fourth to fifth decade of life, and later develop steppage gait and contractures of the hands. Progressive fatty degeneration affects intrinsic muscles of the hands, gluteus medium and both anterior and posterior compartment muscles of the distal lower extremities, with later involvement of forearm muscles, triceps, infraspinatus and the proximal lower limb muscles. Asymmetry of muscle involvement is common.
Autosomal recessive limb-girdle muscular dystrophy type 2L
MedGen UID:
370102
Concept ID:
C1969785
Disease or Syndrome
The spectrum of ANO5 muscle disease is a continuum that ranges from asymptomatic hyperCKemia and exercise-induced myalgia to proximal and/or distal muscle weakness. The most typical presentation is limb-girdle muscular dystrophy type 2L (LGMD2L) with late-onset proximal lower-limb weakness in the fourth or fifth decade (range 15-70 years). Less common is Miyoshi-like disease (Miyoshi muscular dystrophy 3) with early-adult-onset calf distal myopathy (around age 20 years). Incidental hyperCKemia may be present even earlier. Initial symptoms are walking difficulties, reduced sports performance, and difficulties in standing on toes as well as nonspecific exercise myalgia and/or burning sensation in the calf muscles. Muscle weakness and atrophy are frequently asymmetric. Cardiac findings can include cardiomyopathy and arrhythmias and/or left ventricular dysfunction. Bulbar or respiratory symptoms have not been reported. Females have milder disease manifestations than males. Disease progression is slow in both the LGMD and distal forms; ambulation is preserved until very late in the disease course. Life span is normal.
Myofibrillar myopathy 6
MedGen UID:
414119
Concept ID:
C2751831
Disease or Syndrome
Myofibrillar myopathy-6 is an autosomal dominant severe neuromuscular disorder characterized by onset in the first decade of rapidly progressive generalized and proximal muscle weakness, respiratory insufficiency, cardiomyopathy, and skeletal deformities related to muscle weakness. Muscle biopsy shows fiber-type grouping, disruption of the Z lines, and filamentous inclusions, and sural nerve biopsy shows a neuropathy, often with giant axonal neurons. Most patients are severely affected by the second decade and need cardiac transplant, ventilation, and/or a wheelchair (summary by Jaffer et al., 2012). For a phenotypic description and a discussion of genetic heterogeneity of myofibrillar myopathy (MFM), see MFM1 (601419).
Autosomal recessive limb-girdle muscular dystrophy type 2D
MedGen UID:
424706
Concept ID:
C2936332
Disease or Syndrome
Autosomal recessive limb-girdle muscular dystrophy-3 (LGMDR3) affects mainly the proximal muscles and results in difficulty walking. Most individuals have onset in childhood; the disorder is progressive. Other features may include scapular winging, calf pseudohypertrophy, and contractures. Cardiomyopathy has rarely been reported (summary by Babameto-Laku et al., 2011). For a discussion of genetic heterogeneity of autosomal recessive limb-girdle muscular dystrophy, see LGMDR1 (253600).
Mitochondrial DNA depletion syndrome, myopathic form
MedGen UID:
461100
Concept ID:
C3149750
Disease or Syndrome
TK2-related mitochondrial DNA (mtDNA) maintenance defect is a phenotypic continuum that ranges from severe to mild. To date, approximately 107 individuals with a molecularly confirmed diagnosis have been reported. Three main subtypes of presentation have been described: Infantile-onset myopathy with neurologic involvement and rapid progression to early death. Affected individuals experience progressive muscle weakness leading to respiratory failure. Some individuals develop dysarthria, dysphagia, and/or hearing loss. Cognitive function is typically spared. Juvenile/childhood onset with generalized proximal weakness and survival to at least 13 years. Late-/adult-onset myopathy with facial and limb weakness and mtDNA deletions. Some affected individuals develop respiratory insufficiency, chronic progressive external ophthalmoplegia, dysphagia, and dysarthria.
MEGF10-Related Myopathy
MedGen UID:
482309
Concept ID:
C3280679
Disease or Syndrome
EMARDD is a congenital myopathy characterized by proximal and generalized muscle weakness, respiratory difficulties, joint contractures, and scoliosis. More variable features include cleft palate and feeding difficulties. There is variable severity: some patients become ventilator-dependent, never achieve walking, and die in childhood, whereas others have a longer and more favorable course (summary by Logan et al., 2011 and Boyden et al., 2012).
Actin accumulation myopathy
MedGen UID:
777997
Concept ID:
C3711389
Disease or Syndrome
Nemaline myopathy is a form of congenital myopathy characterized by abnormal thread- or rod-like structures in muscle fibers on histologic examination ('nema' is Greek for 'thread'). The clinical phenotype is highly variable, with differing age at onset and severity. Muscle weakness typically involves proximal muscles, with involvement of the facial, bulbar, and respiratory muscles (Ilkovski et al., 2001). Attempts at classification of nemaline myopathies into clinical subtypes have been complicated by the overlap of clinical features and a continuous phenotypic spectrum of disease (North et al., 1997; Wallgren-Pettersson et al., 1999; Ryan et al., 2001; Sanoudou and Beggs, 2001). In general, 2 clinical groups can be readily distinguished: 'typical' and 'severe.' Typical nemaline myopathy is the most common form, presenting as infantile hypotonia and muscle weakness. It is slowly progressive or nonprogressive, and most adults achieve ambulation. The severe form of the disorder is characterized by absence of spontaneous movement or respiration at birth, arthrogryposis, and death in the first months of life. Much less commonly, late-childhood or even adult-onset can occur. However, adult-onset nemaline myopathy is usually not familial and may represent a different disease (Wallgren-Pettersson et al., 1999; Sanoudou and Beggs, 2001). Myopathy caused by mutations in the ACTA1 gene can show a range of clinical and pathologic phenotypes. Some patients have classic rods, whereas others may also show intranuclear rods, clumped filaments, cores, or fiber-type disproportion (see 255310), all of which are nonspecific pathologic findings and not pathognomonic of a specific congenital myopathy. The spectrum of clinical phenotypes caused by mutations in ACTA1 may result from different mutations, modifying factors affecting the severity of the disorder, variability in clinical care, or a combination of these factors (Nowak et al., 1999; Kaindl et al., 2004). Genetic Heterogeneity of Nemaline Myopathy See also NEM1 (609284), caused by mutation in the tropomyosin-3 gene (TPM3; 191030) on chromosome 1q22; NEM2 (256030), caused by mutation in the nebulin gene (NEB; 161650) on chromosome 2q23; NEM4 (609285), caused by mutation in the beta-tropomyosin gene (TPM2; 190990) on chromosome 9p13; NEM5 (605355), also known as Amish nemaline myopathy, caused by mutation in the troponin T1 gene (TNNT1; 191041) on chromosome 19q13; NEM6 (609273), caused by mutation in the KBTBD13 gene (613727) on chromosome 15q22; NEM7 (610687), caused by mutation in the cofilin-2 gene (CFL2; 601443) on chromosome 14q13; NEM8 (615348), caused by mutation in the KLHL40 gene (615340), on chromosome 3p22; NEM9 (615731), caused by mutation in the KLHL41 gene (607701) on chromosome 2q31; NEM10 (616165), caused by mutation in the LMOD3 gene (616112) on chromosome 3p14; and NEM11 (617336), caused by mutation in the MYPN gene (608517) on chromosome 10q21. Several of the genes encode components of skeletal muscle sarcomeric thin filaments (Sanoudou and Beggs, 2001). Mutations in the NEB gene are the most common cause of nemaline myopathy (Lehtokari et al., 2006).
Mitochondrial DNA depletion syndrome 12B (cardiomyopathic type), autosomal recessive
MedGen UID:
815773
Concept ID:
C3809443
Disease or Syndrome
Mitochondrial DNA depletion syndrome-12B is an autosomal recessive mitochondrial disorder characterized by childhood onset of slowly progressive hypertrophic cardiomyopathy and generalized skeletal myopathy resulting in exercise intolerance, and, in some patients, muscle weakness and atrophy. Skeletal muscle biopsy shows ragged-red fibers, mtDNA depletion, and accumulation of abnormal mitochondria (summary by Echaniz-Laguna et al., 2012). For a discussion of genetic heterogeneity of mtDNA depletion syndromes, see MTDPS1 (603041).
Progressive external ophthalmoplegia with mitochondrial DNA deletions, autosomal recessive 1
MedGen UID:
897191
Concept ID:
C4225153
Disease or Syndrome
POLG-related disorders comprise a continuum of overlapping phenotypes that were clinically defined long before their molecular basis was known. Most affected individuals have some, but not all, of the features of a given phenotype; nonetheless, the following nomenclature can assist the clinician in diagnosis and management. Onset of the POLG-related disorders ranges from infancy to late adulthood. Alpers-Huttenlocher syndrome (AHS), one of the most severe phenotypes, is characterized by childhood-onset progressive and ultimately severe encephalopathy with intractable epilepsy and hepatic failure. Childhood myocerebrohepatopathy spectrum (MCHS) presents between the first few months of life and about age three years with developmental delay or dementia, lactic acidosis, and a myopathy with failure to thrive. Other findings can include liver failure, renal tubular acidosis, pancreatitis, cyclic vomiting, and hearing loss. Myoclonic epilepsy myopathy sensory ataxia (MEMSA) now describes the spectrum of disorders with epilepsy, myopathy, and ataxia without ophthalmoplegia. MEMSA now includes the disorders previously described as spinocerebellar ataxia with epilepsy (SCAE). The ataxia neuropathy spectrum (ANS) includes the phenotypes previously referred to as mitochondrial recessive ataxia syndrome (MIRAS) and sensory ataxia neuropathy dysarthria and ophthalmoplegia (SANDO). About 90% of persons in the ANS have ataxia and neuropathy as core features. Approximately two thirds develop seizures and almost one half develop ophthalmoplegia; clinical myopathy is rare. Autosomal recessive progressive external ophthalmoplegia (arPEO) is characterized by progressive weakness of the extraocular eye muscles resulting in ptosis and ophthalmoparesis (or paresis of the extraocular muscles) without associated systemic involvement; however, caution is advised because many individuals with apparently isolated arPEO at the onset develop other manifestations of POLG-related disorders over years or decades. Of note, in the ANS spectrum the neuropathy commonly precedes the onset of PEO by years to decades. Autosomal dominant progressive external ophthalmoplegia (adPEO) typically includes a generalized myopathy and often variable degrees of sensorineural hearing loss, axonal neuropathy, ataxia, depression, parkinsonism, hypogonadism, and cataracts (in what has been called "chronic progressive external ophthalmoplegia plus," or "CPEO+").
Autosomal dominant centronuclear myopathy
MedGen UID:
1645741
Concept ID:
C4551952
Disease or Syndrome
Autosomal dominant centronuclear myopathy is a congenital myopathy characterized by slowly progressive muscular weakness and wasting. The disorder involves mainly limb girdle, trunk, and neck muscles but may also affect distal muscles. Weakness may be present during childhood or adolescence or may not become evident until the third decade of life, and some affected individuals become wheelchair-bound in their fifties. Ptosis and limitation of eye movements occur frequently. The most prominent histopathologic features include high frequency of centrally located nuclei in a large number of extrafusal muscle fibers (which is the basis of the name of the disorder), radial arrangement of sarcoplasmic strands around the central nuclei, and predominance and hypotrophy of type 1 fibers (summary by Bitoun et al., 2005). Genetic Heterogeneity of Centronuclear Myopathy Centronuclear myopathy is a genetically heterogeneous disorder. See also X-linked CNM (CNMX; 310400), caused by mutation in the MTM1 gene (300415) on chromosome Xq28; CNM2 (255200), caused by mutation in the BIN1 gene (601248) on chromosome 2q14; CNM4 (614807), caused by mutation in the CCDC78 gene (614666) on chromosome 16p13; CNM5 (615959), caused by mutation in the SPEG gene (615950) on chromosome 2q35; and CNM6 (617760), caused by mutation in the ZAK gene (609479) on chromosome 2q31. The mutation in the MYF6 gene that was reported to cause a form of CNM, formerly designated CNM3, has been reclassified as a variant of unknown significance; see 159991.0001. Some patients with mutation in the RYR1 gene (180901) have findings of centronuclear myopathy on skeletal muscle biopsy (see 255320).
Myofibrillar myopathy 4
MedGen UID:
1648314
Concept ID:
C4721886
Disease or Syndrome
A rare, genetic, non-dystrophic myofibrillar myopathy disorder characterized by late-adult onset of distal and/or proximal limb muscle weakness with initial involvement of posterior lower leg muscles, medial gastrocnemius and soleus. Patients present with ankle weakness followed by weakness of finger and wrist extensors and later on of proximal muscles. Ambulation is usually preserved. Late-onset associated cardiomyopathy and/or neuropathy has been reported in a minority of cases.
MYH7-related late-onset scapuloperoneal muscular dystrophy
MedGen UID:
1677244
Concept ID:
C4759774
Disease or Syndrome
Oculopharyngodistal myopathy 1
MedGen UID:
1684682
Concept ID:
C5231388
Disease or Syndrome
Myopathy, congenital, with tremor
MedGen UID:
1684886
Concept ID:
C5231401
Disease or Syndrome
Congenital myopathy with tremor (MYOTREM) is an autosomal dominant muscle disorder characterized by onset of hypotonia and tremor in infancy. Patients have mildly delayed walking, unsteady gait, proximal muscle weakness, and a high-frequency tremor of the limbs. Some may develop secondary mild contractures or spinal deformities. Cognition is normal and the disease course tends to stabilize after adolescence (summary by Stavusis et al., 2019).
Neuromuscular disease and ocular or auditory anomalies with or without seizures
MedGen UID:
1684689
Concept ID:
C5231483
Disease or Syndrome
Myopathy, congenital, with respiratory insufficiency and bone fractures
MedGen UID:
1718097
Concept ID:
C5394189
Disease or Syndrome
Congenital myopathy with respiratory insufficiency and bone fractures (MYORIBF) is an autosomal recessive early-onset severe muscular disorder resulting in early death. Affected individuals present at birth with neonatal hypotonia, poor feeding, fractures of the long bones, and respiratory insufficiency. Laboratory investigations are consistent with a defect in early muscle development (summary by Estan et al., 2019).
Oculopharyngodistal myopathy 2
MedGen UID:
1718769
Concept ID:
C5394548
Disease or Syndrome
Oculopharyngodistal myopathy-2 (OPDM2) is an autosomal dominant muscle disorder characterized by onset of distal muscle weakness, mainly of the lower limbs, and/or ophthalmoplegia in the second or third decades of life. The disorder is slowly progressive, and patients develop facial weakness, bulbar weakness, and difficulty walking or climbing stairs. Some patients may have upper limb involvement and subclinical respiratory insufficiency. Laboratory studies show increased serum creatine kinase; skeletal muscle biopsy shows myopathic changes with abnormal cytoplasmic and intranuclear inclusions (summary by Deng et al., 2020). For a discussion of genetic heterogeneity of OPDM, see OPDM1 (164310).
Myopathy, distal, with rimmed vacuoles
MedGen UID:
1728314
Concept ID:
C5399975
Disease or Syndrome
Myofibrillar myopathy 10
MedGen UID:
1769385
Concept ID:
C5436656
Disease or Syndrome
Myofibrillar myopathy-10 (MFM10) is an autosomal recessive structural muscle disorder characterized by onset of muscle pain, cramping, and exercise fatigue in the first or second decades of life. Some patients have mild contractures of the large joints apparent in early childhood. Affected individuals have a characteristic appearance of a thick neck and prominent shoulder girdle with anteverted shoulders and a tendency toward kyphosis. There is no apparent muscle weakness, but some affected individuals show progressive muscle rigidity leading to limited mobility. There is variable cardiac involvement, ranging from chest pain with left ventricular hypertrophy to subclinical signs such as abnormal EKG or elevated cardiac enzymes. Skeletal muscle biopsy shows structural abnormalities with myofibrillar disorganization and accumulation of autophagocytic vacuoles (summary by Hedberg-Oldfors et al., 2020). For a general phenotypic description and a discussion of genetic heterogeneity of myofibrillar myopathy, see MFM1 (601419).
Myofibrillar myopathy 11
MedGen UID:
1782465
Concept ID:
C5543038
Disease or Syndrome
Myofibrillar myopathy-11 (MFM11) is an autosomal recessive skeletal muscle disorder characterized by onset of slowly progressive proximal muscle weakness in the first decade of life. Some patients may present at birth with hypotonia and feeding difficulties, whereas others present later in mid-childhood. Although most patients show delayed walking at 2 to 3 years, all remain ambulatory into adulthood. More variable features may include decreased respiratory forced vital capacity, variable cardiac features, and calf hypertrophy. Skeletal muscle biopsy shows myopathic changes with variation in fiber size, type 1 fiber predominance, centralized nuclei, eccentrically placed core-like lesions, and distortion of the myofibrillary pattern with Z-line streaming and abnormal myofibrillar aggregates or inclusions (summary by Donkervoort et al., 2020). For a phenotypic description and a discussion of genetic heterogeneity of myofibrillar myopathy, see MFM1 (601419).
Neuropathy, hereditary motor, with myopathic features
MedGen UID:
1786836
Concept ID:
C5543119
Disease or Syndrome
Hereditary motor neuropathy with myopathic features (HMNMYO) is an autosomal recessive disorder with both myopathic and neurogenic features. Affected individuals usually present in the first decade with lower leg weakness resulting in difficulty climbing stairs and problems standing on the heels. Some patients have later onset well into the adult years. Most patients have foot deformities, and some may have leg muscle atrophy. The disorder is slowly progressive and often involves the upper limbs. Muscle biopsy and electrophysiologic studies are consistent with both a myopathic process and an axonal motor neuropathy. Sensory abnormalities are not typically present, and patients remain ambulatory. The phenotype shows some phenotypic overlap with distal hereditary motor neuropathy (see, e.g., 182960), but is distinguished by the presence of myopathic features (summary by Deschauer et al., 2021 and Pagnamenta et al., 2021).
Muscular dystrophy, limb-girdle, autosomal recessive 27
MedGen UID:
1794212
Concept ID:
C5562002
Disease or Syndrome
Autosomal recessive limb-girdle muscular dystrophy-27 (LGMDR27) is characterized by progressive muscle weakness primarily affecting the lower limbs and resulting in walking difficulty or loss of ambulation. The age at onset is highly variable, from infancy to young adulthood. Patients with infantile onset may have a more severe disease course with rapid progression. Upper limb involvement and distal muscle weakness may also occur. Additional more variable features include neck muscle weakness, scoliosis, and joint contractures. Less common features include impaired intellectual development or speech delay, cardiomyopathy, and cardiac arrhythmia. Muscle biopsy shows nonspecific dystrophic changes (Coppens et al., 2021). For a discussion of genetic heterogeneity of autosomal recessive limb-girdle muscular dystrophy, see LGMDR1 (253600).

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Schultz-Rogers L, Ferrer A, Dsouza NR, Zimmermann MT, Smith BE, Klee EW, Dhamija R
Cold Spring Harb Mol Case Stud 2019 Dec;5(6) Epub 2019 Dec 13 doi: 10.1101/mcs.a004309. PMID: 31604776Free PMC Article

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