All published cases up to this point where NM is thought to be caused by a mutation in the NEB gene have been autosomal recessive and are the most common cause of nemaline myopathy. Patients with this kind of NM 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 NM may lead to patients having higher intellect.A third kind of nemaline myopathy in the Skeletal Muscle α-Actin Gene ACTA1 is due to a recessive null mutation. These patients do not always show the typical nemaline 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 Nemaline Myopathies. One affects slow skeletal muscles, one leads to the formation of both nemaline bodies and other abnormal, core-like, structures forming in the patients muscles. Diagnosis
Electromyography or (EMG). This procedure determines if nerve or muscle cells are damaged. Since a common symptom of Nemaline Myopathy is muscle weakness this allows doctors to determine where and why the weakness is occurring. MRI of the Musculoskeletal System. MRI uses a magnetic field to take pictures of body structures and allows physicians to determine if a patient has a certain disease. Needle biopsy A needle biopsy allows a physician to test specific cells in the body.
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 NM affect the arrangement of these muscle fibers, causing the muscles to be unable to contract as efficiently or effectively. Nemaline myopathy is usually genetic and shows traits in the affected individual from birth or an early age. However, there are some cases of symptoms of nemaline myopathy not showing up until adulthood. These cases are usually not genetic. Of the genes that have been linked to nemaline myopathy, 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 nemaline myopathy; 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 nemaline myopathies affect the cells and the persons body differently. The first kind of nemaline myopathy identified is due to the Slow α-Tropomyosin Gene TPM3 and varies from case to case with its severity. In this kind of nemaline myopathy, affected people are weaker and more affected in their lower limbs than their upper limbs.As stated above, the most common genetic form of NM is caused by a mutation in the nebulin gene, called Nebulin, and has a range of severity levels.