A rare genetic disorder, named after the presence of rodent formations of nemaline found in the microscope in muscle biopsy. It can either be inherited with an autosomal dominant or recessive pattern or be a sporadic event.
There is a great deal of heterogeneity. Symptoms may start at birth or immediately after or during childhood or more rarely in adulthood. Common symptoms are hypotonia, muscle weakness of the face, neck, shoulder, pelvis and upper parts of the upper and lower limbs with reduced or no reflexes. Due to muscle weakness in the facial muscles, specific features such as a long face, wrong jaw position, speech difficulties are present and there may be problems of swallowing and breathing.
It is divided into six subcategories:
- Common form: concerns 50% of cases and is observed from birth or within the first year of life. Newborns show muscle weakness, which improves over time and hypotonia, eating difficulties (eg dysphagia), muscle weakness in the respiratory muscles leading to respiratory problems. Later there may be problems in leg movement and speech, and rarely distal muscles may be affected in relation to torso’s and lead the person to loss of leg movement and use of a wheelchair. But there is usually independent movement.
- severe neonatal form: evident at birth (16%), where severe muscle weakness and hypotonia, difficulty in swallowing, decreased reflexes and respiratory failure and gastroesophageal reflux are present. Rarely, there is cardiomyopathy, arthrogryposis, fractures, dangerous respiratory failure and respiratory infections.
- Intermediate form: Less severe than neonatal, but more severe than common(20%). There is an early appearance of contractures. Over the years, kids may not be able to stand up or walk independently and be driven to a wheelchair or need permanent respiratory support.
- Children’s form: It presents between the ages of 10 and 20 years old (13%). There is a muscular weakness at the end of puberty that may lead to inability of heel bending and until the age of 40 use of a wheelchair may required.
- Adult form: there is a wide variety of symptoms and concerns only 4% of cases. Symptoms start between the ages of 20 to 50 years, mainly with generalized progressive muscle weakness. Maybe there is muscle pain. Due to the muscle weakness of certain throat muscles there may be a weak head support. Cardiac and respiratory complications rarely occur.
- Amish form. It is only shown in the corresponding community. Symptoms start immediately after birth, with hypotonia, multiple contractions, progressive muscular weakness, deformed and protruding sternum, muscle atrophy and respiratory failure leading to death until the age of 2 years.
- Clinical examination,
- Personal and family history,
- Muscle biopsy,
- Genetic test,
- Ultrasound of muscles.
It is mostly symptomatic and supportive, since there is no cure. For infants, mild exercises, massage and stretching are recommended for muscle strengthening and avoidance of contractions, respiratory support with monitoring and mechanical ventilation and the avoidance of respiratory infections. In addition, feeding tubes can be used and later speech therapy, orthopedic devices and / or interventions, wheelchairs, cardiac monitoring and genetic counseling are recommended.
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- Nemaline Myopathy – Genetics home reference, U.S. National Library of Medicine, https://ghr.nlm.nih.gov/condition/nemaline-myopthy, October 23, 2017.
- Nemaline Myopathy, NORD (National Organization for Rare Disorders), https://rarediseases.org/rare-diseases/nemaline-myopathy/, October 23, 2017.
- Inherited and Endocrine Myopathies – Nemaline Myopathy (rod body disease), Muscular Dystrophy Association, https://www.mda.org/disease/inherited-and-endocrine-myopathies/types/nemaline-myopathy, January 07, 2016.