User:Lukelahood/Myofibrillar myopathy

Myofibrillar myopathy (MFM) is a group of genetic muscle diseases that cause weakness. MFM is distinguished from other genetic muscles diseases by characteristic microscopic findings of muscle.

Signs and symptoms
The various myofibrillary myopathies can result in one of several constellation of signs and symptoms, termed phenotype. These include limb-girdle muscular dystrophy, distal myopathy, scapuloperoneal syndrome or rigid spine syndrome.

In 75% of cases, MFM preferentially weakens the distal muscles, or those of the hands and feet. Otherwise, a the proximal muscles are preferentially affected, a limb-girdle distribution.


 * Respiratory failure
 * Cardiomyopathy

Cause
Each MFM subtype is genetic and defined by the mutated gene. With most genetic disorders, it can be inherited or sporadic. Once a sporadic case occurs, it can then be passed on to future generations. Typically, MFMs are inherited in an autosomal dominant pattern, meaning one mutation is sufficient to cause disease, and each child of an affected parent has a 50% of inheriting the gene and disease.



Pathophysiology
As the name suggests, myofibrillar myopathy causes damage to myofibrils, the rod-shaped components of the cells that make up muscles. Myofibrils are composed of repeating protein structures, called sarcomeres, that are responsible for muscle contraction. Each sarcomere is made up of actin, myosin, and other proteins. The actin is bound together at the Z-disc. The genes implicated in MFM code for proteins founds in the sarcomere, the structural framework (cytoskeleton) outside of the sarcomere, and protein quality control systems.

MFM causes myofibril damage. The first sign is disintegration of the Z-disk region. Subsequently, there is accumulation of degraded proteins in the areas around myofibrils.

Diagnosis
Genetic testing.

Muscle biopsy.

Management
No disease modifying therapeutics are known as of 2016.

History
Discovered in