Congenital Myopathies


Original Editor - Niha Mulla

Top Contributors - Niha Mulla  

Introduction[edit | edit source]

Congenital myopathies are a very broad term of rare disorders present at birth. The term Congenital myopathy is reserved for a group of rare, heterogenous, inherited, primary muscle disorders that cause gross motor delay, poor coordination, and fascial weakness; various orthopedic considerations include foot deformities, joint contractures, hip dysplasia and scoliosis. Congenital myopathy also causes hypotonia and weakness at birth or during the neonatal period and, in some cases, delayed motor development later in childhood.[1][2][3][4][5][6][7]

Description:[edit | edit source]

As described above, Congenital myopathies are rare conditions representing a wide range of disorders in muscle development and function that cause muscle hypotonia and developmental delay. Over twenty genes have been associated with congenital myopathy subtypes.  Facial and respiratory muscle weaknesses are common too.

Congenital myopathy differs in severity, and onset of symptoms. Symptoms can be present from birth, or they can slowly progress throughout the infancy and childhood. [7] [8]

Pathophysiology[edit | edit source]

There are twenty different genes that can be affected in congenital myopathy and the symptoms, of the disease depends on which gene is affected.

As per Matthew Harmelink, MD and team from medspace, “there are variations among each gene and occasionally, these result in phenotypic overlap between genes as well as genes causing congenital myopathy to occasionally have phenotypes more consistent with congenital muscular dystrophies, limb-girdle muscular dystrophies, or even possible neuropathic or neuromuscular junction diseases”. [9]

Epidemiology[edit | edit source]

Congenital myopathies are rare and tend to be less severe than congenital muscular dystrophies. Each type of congenital myopathy is distinguished by an underlying genetic mutation with these disorders have been shown to be inherited in x-linked, autosomal recessive and autosomal dominant forms.[10]

Frequency: The frequency of onset of symptom is found to be 76% during the neonatal period.

Mortality/Morbidity: The largest cause of morbidity and mortality is known to be due to be happening from respiratory and/or feeding failure as a result of muscle function loss.

According to the study by Colombo et al., and as mentioned by  Matthew Harmelink, MD and collogues;  at birth, neonates with congenital myopathy required respiratory support and nasogastric feeding in 30.4% and 25.2% of cases, respectively. And 12% of patients died within the first year, whereas 74.1% achieved independent ambulation with 62.9% being late walkers.[9]

Sex: Congenital myopathy is an extremely rare disorder that generally affects males and females in equal numbers.

Types of Congenital Myopathy[edit | edit source]

There are many types of myopathies that are congenital, some of them seen more commonly than others are listed below:[1][2][3][11][12][13][14]

  1. Nemaline myopathy
  2. Central core myopathy
  3. Centronuclear Myopathy
  4. Congenital Fiber-Type Disproportion
  5. Myosin Storage Myopathy
  6. Multi-mini-core myopathy
  7. Congenital fiber type disproportion myopathy
  8. Myotubular myopathy
  9. Sarco-tubular myopathy
  10. Cylindrical spirals myopathy

Signs & Symptoms[edit | edit source]

Symptoms of congenital myopathy vary depending on the type of congenital myopathy. Also, they can be present at birth or develop throughout infancy and childhood. The most common symptoms of congenital myopathy as follows:[2][3][15]

  • Slow, progressive loss of muscle tone characterized by floppiness (hypotonia).
  • Toddlers with congenital myopathies usually have muscle weakness and is more prone to falling or stumbling.
  • Early motor skills like turning around and sitting up are not met as expected. Also, other critical developmental milestones may be delayed.
  • Most affected muscles are that of pelvis, neck, and shoulder.
  • Difficulty breathing or feeling short of breath is common due to weakness of respiratory muscles.
  • Some babies with congenital myopathy have feeding issues as sucking from breast or bottle and eating with a spoon, chewing and drinking can all be abnormal and difficult.
  • As the symptoms of congenital myopathies are not progressive during adulthood, most people with congenital myopathy walk normally as adults. However, some physical activities may be slightly impaired.

Causes of congenital myopathy[edit | edit source]

Some of the known causes of congenital myopathy are as follows:[2][3]

  • Changes/mutations in specific genes cause congenital myopathies.
  • There is still emerging research on the causes of congenital myopathy as mutations have been found in more than twenty genes, that can potentially cause congenital myopathy.
  • Congenital myopathy follows an autosomal recessive pattern of inheritance. Recessive genetic disorders occurs when an individual inherits a non-working gene from each parent.
  • If an individual receives one working gene and one non-working gene for the disease, the person will be a carrier for the disease, but usually will not show any symptoms.
  • Autosomal recessive forms of congenital myopathy have a typical onset in infancy or childhood and autosomal dominant forms have the mildest symptoms and may present in adulthood.

Evaluation and diagnosis[edit | edit source]

There are barely any specific tests to directly diagnose congenital myopathy other than muscle biopsy. Though following tests are vital for diagnosis.[1][2][3][14][10]

  • Blood test is done to check for increased levels of a muscle enzyme called creatine kinase.
  • An Electromyography (EMG)and nerve conduction studies is done to measure the electrical activity of the muscle.
  • A muscle biopsy is the most important test that looks up the structure of the muscle to look at the muscle changes specific to congenital myopathy.
  • Genetic DNA testing is sometimes done depending on the clinical evaluation as it looks for changes in the genes that caused myopathy.
  • Pulmonary function studies/sleep studies and pulmonary function tests are performed as congenial myopathy weakens the respiratory muscles along with other skeletal muscles further causing breathing and feeding difficulty.
  • Diagnosis of congenital myopathies is also suggested by characteristic clinical findings which are also confirmed by MRI of muscles.

Differential Diagnosis[edit | edit source]

Prognosis[edit | edit source]

The prognosis for congenital myopathies widely varies depending on the type and severity of myopathy. In most severe cases newborns/ infants may die due to the severity of myopathy, while some types of congenital myopathies only result in mild weakness and some effects on activities of daily living.[3][9]

Treatment[edit | edit source]

  • Patient education is vital, genetic counseling is helpful to make family planning decisions. And most importantly, the current mainstay of treatment is supportive care as there are no current treatments for the underlying genetic mutations.[3][10]
  • (Robb 2011) Gene therapy studies in animal models have been promising for certain subtypes of congenital myopathy, but there are no current gene therapies approved for human use. (Dastgir 2018) [3][10] [16][17]
  • Treatment for central core disease and multicore disease may involve the use of a drug called albuterol which is considered experimental and only gives symptomatic relief, but has been shown to considerably reduce weakness in children.  However, it is also important to know it is not cure.[3]
  • Congenial myopathy has no cure, hence treatment for all types of congenital myopathy remains focused on managing the symptoms. These treatments include; orthopedic treatment, physical therapy, occupational therapy, speech therapy, other medical and surgical interventions and psychological support.[3][9]
  • The focus of medical care is to evaluate and slow the progression of the disease as well as the symptoms.[3]
  • Pulmonary treatment includes evaluation of signs of hypoventilation at night, including morning headaches, snoring, or daytime sleepiness. As respiratory support for frequent or prolonged respiratory issues  may be necessary.
  • Surgical Care might be essential for contractures, foot deformities and scoliosis in some severely affected cases.
  • Gastrostomy tube is sometimes needed for newborns with feeding difficulties. And in some cases due to facial and bulbar muscle weakness, patients may require assistance through feeding therapy.[9]
  • Patient suffering from congenial myopathy are at a high risk for respiratory compromise, cardiomyopathy and may be at risk for malignant hyperthermia. Hence, consistent evaluation of patient condition from time to time is essential.
  • The decision to proceed with any kind and form of surgical management should be made with consideration of the patient’s underlying health issues, quality of life, and surgical risk as at most times, in patients with congenial myopathy post-surgical complication out way the benefits of the surgery; by further increasing the muscle weakness at and around proximal and distal attachments of the point of surgery.  [9]
  • Speech therapy is recommended to help with delayed speech.[3]
  • Nutrition therapy is important to make sure congenital myopathy patients are getting the nutrition they need as most of them suffer from feeding difficulty as infants.[9]

Physiotherapy Interventions[edit | edit source]

  • Research have shown that surgical treatment in the backdrop of a congenital myopathy in many instances worsens the patient’s underlying muscle weakness. Hence, physical and occupational therapy are the first line of treatment for most cases of congenital myopathy.[3]
  • Main goal of physical therapy management is maintaining activities of daily living and have continued functional ability for the patients, with independence to do the daily living activities with minimal or no support.[9]
  • During each visit of the patient, treatment should be directed towards the chief complaint of the patient, but should also involve a complete assessments of muscle function, contractures, patients  ability to perform activities of daily living and cardiopulmonary function to set the long term goals of management.[17]
  • Contractures and foot deformities should be managed with stretching and bracing.[10]
  • Initially, physical therapy exercises are focused on, improving the range of motion of joints and strengthening core muscles.
  • The treatment of muscle weakness revolves around stretching, bracing, and supportive care. However, bracing is some instances is contraindicated as immobility can result in worsening of muscle weakness.[9]
  • Assistive devices are considered as a good option when weakness is severe enough to hamper the activities of daily living.[9][10]
  • Congenital myopathy patient should be well evaluated for presence of scoliosis, as it can further put more strain on the weakened respiratory system.
  • Respiratory muscle strengthening is important to maintain normal breathing in patients with congenial myopathy.[9]
  • Further, the exercises should emphasis on improving balance and fine motor skills (use of hand and fingers)[18]

References[edit | edit source]

  1. 1.0 1.1 1.2 Congenital myopathy. Wikipedia. Wikimedia Foundation; 2021. Available from: https://en.wikipedia.org/wiki/Congenital_myopathy
  2. 2.0 2.1 2.2 2.3 2.4 2.5 Congenital myopathy. NORD (National Organization for Rare Disorders). 2020. Available from: https://rarediseases.org/rare-diseases/myopathy-congenital-batten-turner-type/#:~:text=Congenital%20myopathy%20(CM)%20is%20an,(mutations)%20in%20specific%20genes.
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 Congenital myopathies: Symptoms, causes & outlook. Cleveland Clinic. Available from: https://my.clevelandclinic.org/health/diseases/22392-congenital-myopathy
  4. Lossin C, George Jr AL. Myotonia congenita. Advances in genetics. 2008 Jan 1;63:25-55.
  5. Sewry CA, Jimenez-Mallebrera C, Muntoni F. Congenital myopathies. Current opinion in neurology. 2008 Oct 1;21(5):569-75.
  6. Romero NB, Clarke NF. Congenital myopathies. Handbook of clinical neurology. 2013 Jan 1;113:1321-36.
  7. 7.0 7.1 Nance JR, Dowling JJ, Gibbs EM, Bönnemann CG. Congenital myopathies: an update. Current neurology and neuroscience reports. 2012 Apr;12(2):165-74.
  8. Bodamer O, Patterson M, Dashe J. Congenital myopathies. UpToDate.. Available from: https://www.uptodate.com/contents/congenital-myopathies
  9. 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 Matthew Harmelink MD. Congenital myopathies. Background, Pathophysiology, Epidemiology. Medscape; 2019. Available from: https://emedicine.medscape.com/article/1175852-overview
  10. 10.0 10.1 10.2 10.3 10.4 10.5 Hubbard E. Congenital myopathy. POSNA: Pediatric orthopedic society of north America. Available from: https://posna.org/Physician-Education/Study-Guide/Congenital-Myopathy
  11. National Organization for Rare Disorders. Congenital Myopathy. Available from: https://rarediseases.org/rare-diseases/myopathy-congenital-batten-turner-type/
  12. National Institute of Neurological Disorders and Stroke. Congenital Myopathy Information Page. Available from: https://www.ninds.nih.gov/Disorders/All-Disorders/Congenital-Myopathy-Information-Page
  13. Congenital myopathies. Congenital myopathies | Muscular Dystrophy UK. Available from: https://www.musculardystrophyuk.org/conditions/congenital-myopathies
  14. 14.0 14.1 14.2 Nagy H, Veerapaneni KD. Myopathy. InStatPearls 2021 Sep 1. StatPearls Publishing.
  15. Rubin M. Congenital myopathies - pediatrics. Merck Manuals Professional Edition. Merck Manuals; 2022. Available from: https://www.merckmanuals.com/professional/pediatrics/inherited-muscular-disorders/congenital-myopathies
  16. Robb SA, Sewry CA, Dowling JJ, et al.: Impaired neuromuscular transmission and response to acetylcholinesterase inhibitors in centronuclear myopathies. Neuromuscul Disord 2011;21:379-386.
  17. 17.0 17.1 Dastgir J, Gonorazky HD, Strober JB, Chrestian N, Dowling JJ: Congenital Myopathies, in Swaiman KF, Ashwal S, Ferriero DM, et al. (eds): Swaiman's pediatric neurology : principles and practice, ed Sixth edition. Edinburgh ; New York: Elsevier,, 2018, pp xxvi, 1403 pages.
  18. Phillips BA, Mastaglia FL. Exercise therapy in patients with myopathy. Current Opinion in Neurology. 2000 Oct 1;13(5):547-52.