Laing distal myopathy
Alternate names[edit | edit source]
Laing early-onset distal myopathy; Myopathy distal, type 1
Definition[edit | edit source]
Laing distal myopathy is a slowly progressive muscle disorder that tends to begin in childhood.
Epidemiology[edit | edit source]
Although Laing distal myopathy is thought to be rare, its prevalence is unknown. Several families with the condition have been identified worldwide.
Cause[edit | edit source]
Laing distal myopathy is caused by mutations in the MYH7 gene. The MYH7 gene provides instructions for making a protein that is found in heart (cardiac) muscle and in type I skeletal muscle fibers. In cardiac and skeletal muscle cells, the protein produced from the MYH7 gene forms part of a larger protein called type II myosin.
Gene mutations[edit | edit source]
- Researchers have proposed that these mutations alter the structure of myosin in skeletal muscles, which prevents it from interacting with other proteins.
- The abnormal myosin gradually impairs the function of type I skeletal muscle fibers.
Inheritance[edit | edit source]
This condition is inherited in an autosomal dominant fashion.
Signs and symptoms[edit | edit source]
- Early symptoms include weakness in the feet and ankles, followed by weakness in the hands and wrists.
- Weakness in the feet leads to tightening of the Achilles tendon, an inability to lift the big toe, and a high-stepping walk.
- Weakness in the hands makes it more difficult to lift the fingers, especially the third and fourth fingers.
- As the muscle weakness slowly progresses over the course of many years, other muscles of the body (e.g., neck, face, legs, hips, and shoulders) weaken.
- Other findings include scoliosis and cardiomyopathy in up to one third of individuals.
Clinical presentation[edit | edit source]
For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.
80%-99% of people have these symptoms
- Foot dorsiflexor weakness(Foot drop)
- Toe extensor amyotrophy
30%-79% of people have these symptoms
- Abnormal mitochondria in muscle tissue
- Abnormality of the calf musculature(Abnormal calf muscles)
- Distal muscle weakness(Weakness of outermost muscles)
- Gait disturbance(Abnormal gait)
- High palate(Elevated palate)
- Mildly elevated creatine kinase
- Minicore myopathy
- Myalgia(Muscle ache)
- Neck muscle weakness(Floppy neck)
- Progressive muscle weakness
- Scoliosis
- Talipes cavus equinovarus
- Type 1 muscle fiber predominance
- Weakness of orbicularis oculi muscle
5%-29% of people have these symptoms
- Dilated cardiomyopathy(Stretched and thinned heart muscle)
- EMG: myopathic abnormalities
- Proximal muscle weakness(Weakness in muscles of upper arms and upper legs)
- Proximal muscle weakness in lower limbs
Diagnosis[edit | edit source]
The diagnosis of Laing distal myopathy is established in a proband with suggestive findings and a heterozygous pathogenic variant in MYH7 identified by molecular genetic testing.[1][1]. Laboratory findings
- Serum creatine kinase concentration is usually normal, but may in rare cases be as high as eight times the upper limit of normal.
- Nerve conduction studies are normal.
- Electromyographic findings are nonspecific, with occasional fibrillation potentials but no prolonged or large motor unit potentials
Treatment[edit | edit source]
- Treatment may include physiotherapy to prevent tightening of the Achilles tendon and splinting of the ankle.[2][2].
- Annual neurologic examinations, evaluations for scoliosis, and regular assessments of cardiac and respiratory functions may be necessary.
References[edit | edit source]
- ↑ Lamont P, Laing NG. Laing Distal Myopathy. 2006 Oct 17 [Updated 2021 Feb 4]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2021. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1433/
- ↑ Lamont P, Laing NG. Laing Distal Myopathy. 2006 Oct 17 [Updated 2021 Feb 4]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2021. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1433/
NIH genetic and rare disease info[edit source]
Laing distal myopathy is a rare disease.
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