Muscle cells contract in complex mechanical and chemical processes. If any part of the process or structure is disrupted, dysfunction will likely result, as in the case of those with genetic variations. In those with<unk> , muscle contraction is adversely affected. At the electron microscopic level, rod-shaped components can often be seen in some of the muscle cells, and when seen, are diagnostic for the condition called<unk>  rod myopathy. The presence of these rods is not itself causing muscle weakness; rather they appear as a result of something going wrong within the muscle fiber. There is no connection between the number of rods found in the muscle cells and the amount of weakness a person has. All of the different gene mutations leading to the condition called<unk>  that have been found so far are in genes that encode different components of the sarcomere. In normal muscle cells, the various parts of the muscle fibers that make up the sarcomere are distributed evenly in a pattern for effective muscle contraction. Evidence suggests that some kinds of<unk>  affect the arrangement of these muscle fibers, causing the muscles to be unable to contract as efficiently or effectively. This is a simple example of a healthy sarcomere. Example of a sarcomere with<unk>  rods.<unk>  is usually genetic and shows traits in the affected individual from birth or an early age. However, there are some cases of symptoms of<unk>  not showing up until adulthood. These cases are usually not genetic. Of the genes that have been linked to<unk> , most are also involved in encoding proteins in the sarcomeres in the muscle cells. Respiratory muscles are often more affected than other skeletal muscle groups. Cardiac muscle is usually not affected in<unk> ; however, in cases where it does, patients often present with dilated cardiomyopathy. The ocular muscles are usually spared. The different genes whose mutations lead to the different kinds of<unk> es affect the cells and the person's body differently. The first kind of<unk>  identified is due to the Slow α-Tropomyosin Gene TPM3 and varies from case to case with its severity. In this kind of<unk> , affected people are weaker and more affected in their lower limbs than their upper limbs. As stated above, the most common genetic form of<unk>  is caused by a mutation in the nebulin gene, called Nebulin, and has a range of severity levels. All published cases up to this point where<unk>  is thought to be caused by a mutation in the NEB gene have been autosomal recessive and are the most common cause of<unk> . Patients with this kind of<unk>  are more affected in the muscles in their head, rather than their proximal muscles at the core of their body. Consequently, patients with this genetic mutation often cannot lift their heads and speak with a nasal voice. There have been cases that suggest this kind of<unk>  may lead to patients having higher intellect. A third kind of<unk>  in the Skeletal Muscle α-Actin Gene ACTA1 is due to a recessive null mutation. These patients do not always show the typical<unk>  bodies in their muscle cells. The only abnormality they show is an abnormal distribution of muscle fibers. There are several other identified kinds of mutations that lead to<unk> es. One affects slow skeletal muscles, one leads to the formation of both<unk>  bodies and other abnormal, core-like, structures forming in the patient's muscles.
Nemaline myopathy
Brody myopathy
Centronuclear myopathy
Bethlem myopathy
Muscular dystrophy
Metabolic myopathy
Inflammatory myopathy
Hereditary inclusion body myopathy