The exact mechanisms of these diseases are not well understood. GNE/MNK a key enzyme in the sialic acid biosynthetic pathway, and loss-of-function mutations in GNE/MNK may lead to a lack of sialic acid, which in turn could affect sialoglycoproteins. GNE knockout mice show problems similar to people with IBM and in people with IBM dystroglycan has been found to lack sialic acid. However, the part of the dystroglycan that is important in muscle function does not seem to be affected. Another protein, neural cell adhesion molecule is under-sialyated in people with IBM, but as of 2016 it had no known role in muscle function.

It is not uncommon for drugs to damage muscle fibers. Particular families of drugs are known to induce myopathies on the molecular level, thus altering organelle function such as the mitochondria. Use of multiple drugs from these families in conjunction with one another can increase the risk of developing a myopathy. Many of the drugs associated with inducing myopathies in patients are found in rheumatology practice.

New research resources have become available for the NM community, such as the CMDIR (registry) and the CMD-TR (biorepository). These two resources connect families and individuals interested in participating in research with the scientists that aim to treat or cure NM. Some research on NM seeks to better understand the molecular effects the gene mutations have on muscle cells and the rest of the body and to observe any connections NM may have to other diseases and health complications.

The different forms have different mutations and inheritance patterns. See the detailed OMIM descriptions for details (given above).

The overall incidence of myotubular myopathy is 1 in 50,000 male live births. The incidence of other centronuclear myopathies is extremely rare, with there only being nineteen families identified with CNM throughout the world. The symptoms currently range from the majority who only need to walk with aids, from a stick to a walking frame, to total dependence on physical mobility aids such as wheelchairs and stand aids, but this latter variety is so rare that only two cases are known to the CNM "community".

Approximately 80% of males with a diagnosis of myotubular myopathy by muscle biopsy will have a mutation in MTM1 identifiable by genetic sequence analysis.

Many patients with myotubular myopathy die in infancy prior to receiving a formal diagnosis. When possible, muscle biopsy and genetic testing may still be helpful even after a neonatal death, since the diagnostic information can assist with family planning and genetic counseling as well as aiding in the accurate diagnosis of any relatives who might also have the same genetic abnormality.

While the exact incidence is unknown, estimates range from 33 - 57 percent of patients staying in the ICU for longer than 7 days. More exact data is difficult to obtain, since variation exists in defining the condition.

The three main risk factors for CIP and CIM are sepsis and systemic inflammatory response syndrome (SIRS), and multi-organ failure. Reported rates of CIP/CIM in people with sepsis and SIRS range from 68 to 100 percent. Additional risk factors for developing CIP/CIM include: female gender, high blood sugar (hyperglycemia), low serum albumin, and immobility. A greater severity of illness increases the risk of CIP/CIM. Such risk factors include: multi-organ dysfunction, renal failure, renal replacement therapy, duration of organ dysfunction, duration of ICU stay, low albumin, and central neurologic failure.

Certain medications are associated with CIP/CIM, such as corticosteroids, neuromuscular blocking agents, vasopressors, catecholamines, and intravenous nutrition (parenteral nutrition). Research has produced inconsistent results for the impact of hypoxia, hypotension, hyperpyrexia, and increased age on the risk of CIP/CIM. The use of aminoglycosides is "not" an independent risk for the development of CIP/CIM.

Bethlem myopathy is an autosomal dominant myopathy, classified as a congenital form of muscular dystrophy, that is caused by a mutation in one of the three genes coding for type VI collagen. These include COL6A1, COL6A2, and COL6A3.

The Food and Drug Administration is recommending that physicians restrict prescribing high-dose Simvastatin (Zocor, Merck) to patients, given an increased risk of muscle damage. The FDA drug safety communication stated that physicians should limit using the 80-mg dose unless the patient has already been taking the drug for 12 months and there is no evidence of myopathy.

"Simvastatin 80 mg should not be started in new patients, including patients already taking lower doses of the drug," the agency states.

Acquired noninflammatory myopathy can be caused by a variety of factors including metabolic abnormalities, drugs, nutritional deficiency, trauma, and upstream abnormalities resulting in decreased function. Two of the most common causes of ANIM are hyperthyroidism and excessive steroid use, while many drugs used to treat rheumatism are known to be inducing agents. Most cases of ANIM can be linked to drugs or dietary abnormalities.

Distal muscular dystrophy (or distal myopathy) is a group of disorders characterized by onset in the hands or feet. Many types involve dysferlin, but it has been suggested that not all cases do.

Types include:

DYSF is also associated with limb-girdle muscular dystrophy type 2B.

Distal muscular dystrophy is a type of muscular dystrophy that affects the muscles of the extremities, the hands, feet, lower arms, or lower legs. The cause of this dystrophy is very hard to determine because it can be a mutation in any of at least eight genes and not all are known yet. These mutations can be inherited from one parent, autosomal dominant, or from both parents, autosomal recessive. Along with being able to inherit the mutated gene, distal muscular dystrophy has slow progress therefore the patient may not know that they have it until they are in their late 40’s or 50’s. There are eight known types of distal muscular dystrophy. They are Welander’s distal myopathy, Finnish (tibial) distal myopathy, Miyoshi distal myopathy, Nonaka distal myopathy, Gowers–Laing distal myopathy, hereditary inclusion-body myositis type 1, distal myopathy with vocal cord and pharyngeal weakness, and ZASP-related myopathy. All of these affect different regions of the extremities and can show up as early as 5 years of age to as late as 50 years old. Doctors are still trying to determine what causes these mutations along with effective treatments.

There is no specific treatment but triggering anesthetics are avoided and relatives are screened for "RYR1" mutations as these may make them susceptible to MH.

The onset of this disease can begin even before birth but is more commonly in childhood or later into adult life. The progression is slow, with symptoms of weakness and walking difficulties sometimes not presenting until middle age. Early symptoms include Gower's sign ("climbing" up the thighs with the hands when rising from the floor) and tiptoe-walking caused by the beginning of contractures.

Bethlem myopathy affects about 1 in 200,000 people. Contractures of the fingers are a typical symptom of Bethlem myopathy but not of the related Ullrich's myopathy (which does include contractures of arms and legs, as does Bethlem myopathy). Serum creatine kinase is elevated in Bethlem myopathy, as there is ongoing muscle cell death. Patients with Bethlem myopathy may expect a normal life span and continued mobility into adulthood. There is currently no cure for this disorder, but the contractures of the legs can be alleviated with heel-cord surgery followed by bracing and regular physical therapy. Repeated surgeries to lengthen the heel cords may be needed as the child grows to adulthood.

Central core disease (CCD), also known as central core myopathy, is an autosomal dominant congenital myopathy (inborn muscle disorder). It was first described by Shy and Magee in 1956. It is characterized by the appearance of the myofibril under the microscope.

Although there is no cure for NM, it is possible, and common for many people live healthy active lives even with moderate to severe cases. Research continues to seek ways to ameliorate debilitating symptoms and lengthen the life-span in quality ways for those affected. Some people have seen mild improvements in secretion handling, energy level, and physical functioning with supplemental L-tyrosine, an amino acid that is available through health centers. Some symptoms may worsen as the patient ages. Muscle loss increases with age naturally, but it is even more significant with nemaline myopathy.

Although no cure currently exists, there is hope in treatment for this class of hereditary diseases with the use of an embryonic mitochondrial transplant.

Meige lymphedema, also known as Meige disease, Late-onset lymphedema, and Lymphedema hereditary type 2, is an inherited disease in which patients develop lymphedema. The onset is between the ages of 1 and 35. Other causes of primary lympoedema include Milroy's disease which occurs before the age of 1, and lymphoedema tarda which occurs after the age of 35.

Meige disease,(Hereditary lymphedema type II), has its onset around the time of puberty. It is an autosomal dominant disease. It has been linked to a mutations in the ‘forkhead’ family transcription factor (FOXC2) gene located on the long arm of chromosome 16 (16q24.3). It is the most common form of primary lymphedema, and about 2000 cases have been identified. Meige disease usually causes lymphedema of the legs, however, other areas of the body may be affected, including the arms, face and larynx. Yellow toe nails occur in some individuals.

Inclusion body myositis (IBM) is an inflammatory muscle disease characterized by slowly progressive weakness and wasting of both distal and proximal muscles, most apparent in the muscles of the arms and legs. There are two types: sporadic inclusion body myositis (sIBM), which is more common, and hereditary inclusion body myopathy (hIBM).

In sporadic inclusion body myositis [MY-oh-sigh-tis], two processes, one autoimmune and the other degenerative, appear to occur in the muscle cells in parallel. The inflammation aspect is characterized by the cloning of T cells that appear to be driven by specific antigens to invade muscle fibers. The degeneration aspect is characterized by the appearance of holes in the muscle cell vacuoles, deposits of abnormal proteins within the cells and in filamentous inclusions (hence the name inclusion body myositis).

Weakness comes on slowly (over months or years) and progresses steadily and usually leads to severe weakness and wasting of arm and leg muscles. It is more common in men than women. Patients may become unable to perform activities of daily living and most require assistive devices within 5 to 10 years of symptom onset. sIBM is not considered a disorder, but the risk of serious injury due to falls is increased. One common and potentially fatal complication is dysphagia. There is no effective treatment for the disease.

sIBM is a rare yet increasingly prevalent disease and is the most common cause of inflammatory myopathy in people over age 50. Recent research from Australia indicates that the incidence of IBM varies in different populations and ethnic groups. The authors found that the current prevalence was 14.9 per million in the overall population, with a prevalence of 51.3 per million population in people over 50 years of age. As seen in these numbers, sIBM is an age-related disease – its incidence increases with age and symptoms usually begin after 50 years of age. It is the most common acquired muscle disorder seen in people over 50, although about 20% of cases display symptoms before the age of 50.

Myotubular myopathy, also known as centeronuclear myopathy, is recognized by pain during exercise and difficulty walking. People affected by this disease typically are wheel-chair-bound by middle adulthood, have weakness in the muscles involved in eye movement, nerve function disorders, and some form of intellectual disability. Myotubular myopathy is very rare, with less than 50 families currently affected.

Genetically, myotubular myopathy can have two causes: autosomal dominant and autosomal recessive. When caused by a mutation in the DNM2 gene, the disorder is autosomal dominant, meaning it can be passed on by one mutated gene. When the mutation takes place in the BIN1 gene, the disease is instead autosomal recessive, and both genes must be mutated for the disease to be inherited. Autosomal recessive onset is most common.

At DeathMlg

None as systemic causes; mainly hereditary

Onset in childhood

Inflammatory myopathies – dermatomyositis, polymyositis (rarely)

Infectious myopathies

Endocrine and metabolic disorders – hypokalemia, hypocalcemia, hypercalcemia

Onset in adulthood

Inflammatory myopathies – polymyositis, dermatomyositis, inclusion body myositis, viral (HIV)

Infectious myopathies

Endocrine myopathies – thyroid, parathyroid, adrenal, pituitary disorders

Toxic myopathies – alcohol, corticosteroids, narcotics, colchicines, chloroquine

Critical illness myopathy

Metabolic myopathies

Paraneoplastic myopathy

Limb girdle syndrome is a term to describe several distinct medical conditions including polymyositis, myopathy associated with endocrine disease, metabolic myopathy, drug-induced myopathy and limb-girdle muscular dystrophy.

Limb girdle syndrome is weakness located and concentrated around the proximal limb muscles. There are many causes, manifestations and treatments.

Currently there is no cure for myotubular or centronuclear myopathies. Treatment often focuses on trying to maximize functional abilities and minimize medical complications, and involvement by physicians specializing in Physical Medicine and Rehabilitation, and by physical therapists and occupational therapists.

Medical management generally involves efforts to prevent pulmonary complications, since lung infections can be fatal in patients lacking the muscle strength necessary to clear secretions via coughing. Medical devices to assist with coughing help patients maintain clear airways, avoiding mucous plugs and avoiding the need for tracheostomy tubes.

Monitoring for scoliosis is also important, since weakness of the trunk muscles can lead to deviations in spinal alignment, with resultant compromise of respiratory function. Many patients with congenital myopathies may eventually require surgical treatment of scoliosis.

Congenital fiber type disproportion (CFTD) is an inherited form of myopathy with small type 1 muscle fibers that may occur in a number of neurological disorders. It has a relatively good outcome and follows a stable course. While the exact genetics is unclear there is an association with TPM3, ACTA1 and SEPN1 gene mutations. It is a rare condition.

Five different clinical entities have been described under hereditary sensory and autonomic neuropathies – all characterized by progressive loss of function that predominantly affects the peripheral sensory nerves. Their incidence has been estimated to be about 1 in 25,000.

The cause of IBM is unknown. IBM likely results from the interaction of a number of genetic and environmental factors.

There are two major theories about how sIBM is caused. One hypothesis suggests that the inflammation-immune reaction, caused by an unknown trigger – likely an undiscovered virus or an autoimmune disorder– is the primary cause of sIBM and that the degeneration of muscle fibers and protein abnormalities are secondary features. Despite the arguments "in favor of an adaptive immune response in sIBM, a purely autoimmune hypothesis for sIBM is untenable because of the disease's resistance to most immunotherapy."

The second school of thought advocates the theory that sIBM is a degenerative disorder related to aging of the muscle fibers and that abnormal, potentially pathogenic protein accumulations in myofibrils play a key causative role in sIBM (apparently before the immune system comes into play). This hypothesis emphasizes the abnormal intracellular accumulation of many proteins, protein aggregation and misfolding, proteosome inhibition, and endoplasmic reticulum (ER) stress.

One review discusses the "limitations in the beta-amyloid-mediated theory of IBM myofiber injury."

Dalakas (2006) suggested that a chain of events causes IBM—some sort of virus, likely a retrovirus, triggers the cloning of T cells. These T cells appear to be driven by specific antigens to invade muscle fibers. In people with sIBM, the muscle cells display “flags” telling the immune system that they are infected or damaged (the muscles ubiquitously express MHC class I antigens) and this immune process leads to the death of muscle cells. The chronic stimulation of these antigens also causes stress inside the muscle cell in the endoplasmic reticulum (ER) and this ER stress may be enough to cause a self-sustaining T cell response (even after a virus has dissipated). In addition, this ER stress may cause the misfolding of protein. The ER is in charge of processing and folding molecules carrying antigens. In IBM, muscle fibers are overloaded with these major histocompatibility complex (MHC) molecules that carry the antigen protein pieces, leading to more ER stress and more protein misfolding.

A self-sustaining T cell response would make sIBM a type of autoimmune disorder. When studied carefully, it has not been impossible to detect an ongoing viral infection in the muscles. One theory is that a chronic viral infection might be the initial triggering factor setting IBM in motion. There have been a handful of IBM cases—approximately 15—that have shown clear evidence of a virus called HTLV-1. The HTLV-1 virus can cause leukemia, but in most cases lies dormant and most people end up being lifelong carriers of the virus. One review says that the best evidence points towards a connection with some type of retrovirus and that a retroviral infection combined with immune recognition of the retrovirus is enough to trigger the inflammation process.

- amyloid protein

- The hypothesis that beta amyloid protein is key to IBM has been supported in a mouse model using an Aβ vaccine that was found to be effective against inclusion body myositis in mouse models. Although this vaccine is likely not safe for human use, it still shows that attacking Aβ has efficacy in mice against IBM.

- Following up on earlier leads, the Greenberg group report finding that the protein TDP-43 is a very prominent and highly sensitive and specific feature of IBM. This protein is normally found within the nucleus but in IBM is found in the cytoplasm of the cell. This important advance should help develop a new screening technique for IBM and may provide clues in terms of a therapeutic approach

Central core disease or central core myopathy was first described in 1956 and usually presents in infancy or early childhood as non-progressive mild proximal weakness that persists throughout life. Central core disease is believed to be more prevalent than currently reported, as it is hard to recognize and often misdiagnosed in early childhood. Central core disease has been found to be allelic with malignant hyperthermia, which is a life-threatening anesthetic reaction that causes a rise in body temperature, muscular rigidity and muscular breakdown, grossly elevated creatine kinase, and acidosis. Central core disease is caused by a mutation in the RYR1 gene.