Myopathy

# Overview
In medicine, a myopathy is a neuromuscular disease in which the muscle fibers do not function for any one of many reasons, resulting in muscular weakness. "Myopathy" simply means muscle disease (myo- Greek  "muscle" + pathy Greek "suffering"). This meaning implies that the primary defect is within the muscle, as opposed to the nerves ("neuropathies" or "neurogenic" disorders) or elsewhere (e.g., the brain etc.). Muscle cramps, stiffness, and spasm can also be associated with myopathy.

# Classes
Because myopathy is such a general term, there are several classes of myopathy.... (ICD-10 codes are provided where available.)
- (G71.0) Dystrophies (or muscular dystrophies) are a subgroup of myopathies characterized by muscle degeneration and regeneration. Clinically, muscular dystrophies are typically progressive, because the muscles' ability to regenerate is eventually lost, leading to progressive weakness, often leading to use of a wheelchair, and eventually death, usually related to respiratory weakness.
- (G71.1) Myotonia
Neuromyotonia
- Neuromyotonia
- (G71.2) The congenital myopathies do not show evidence for either a progressive dystrophic process (i.e., muscle death) or inflammation, but instead characteristic microscopic changes are seen in association with reduced contractile ability of the muscles. Among others, different congenital myopathies include:
(G71.2) nemaline myopathy (characterized by presence of "nemaline rods" in the muscle),
(G71.2) multi/minicore myopathy (characterized by multiple small "cores" or areas of disruption in the muscle fibers),
(G71.2) centronuclear myopathy (or myotubular myopathy) (in which the nuclei are abnormally found in the center of the muscle fibers) is a rare muscle wasting disorder that occurs in three forms:
The most severe form is present at birth, which is inherited as an X-linked genetic trait, and can cause severe respiratory muscle weakness. This is the form of centronuclear myopathy currently referred to as myotubular myopathy.
A less severe form of centronuclear myopathy that may present itself at birth or in early childhood progresses slowly and is inherited as an autosomal recessive genetic trait.
The least severe of the three forms of centronuclear myopathy first appears during the second and third decades of life and is slowly progressive; it is inherited as an autosomal dominant genetic trait.
- (G71.2) nemaline myopathy (characterized by presence of "nemaline rods" in the muscle),
- (G71.2) multi/minicore myopathy (characterized by multiple small "cores" or areas of disruption in the muscle fibers),
- (G71.2) centronuclear myopathy (or myotubular myopathy) (in which the nuclei are abnormally found in the center of the muscle fibers) is a rare muscle wasting disorder that occurs in three forms:
The most severe form is present at birth, which is inherited as an X-linked genetic trait, and can cause severe respiratory muscle weakness. This is the form of centronuclear myopathy currently referred to as myotubular myopathy.
A less severe form of centronuclear myopathy that may present itself at birth or in early childhood progresses slowly and is inherited as an autosomal recessive genetic trait.
The least severe of the three forms of centronuclear myopathy first appears during the second and third decades of life and is slowly progressive; it is inherited as an autosomal dominant genetic trait.
- The most severe form is present at birth, which is inherited as an X-linked genetic trait, and can cause severe respiratory muscle weakness. This is the form of centronuclear myopathy currently referred to as myotubular myopathy.
- A less severe form of centronuclear myopathy that may present itself at birth or in early childhood progresses slowly and is inherited as an autosomal recessive genetic trait.
- The least severe of the three forms of centronuclear myopathy first appears during the second and third decades of life and is slowly progressive; it is inherited as an autosomal dominant genetic trait.
- (G71.3) Mitochondrial myopathies are due to defects in mitochondria, which provide a critical source of energy for muscle.
- (G72.3) Familial periodic paralysis
- (G72.4) Inflammatory myopathies are caused by problems with the immune system attacking components of the muscle, leading to signs of inflammation in the muscle.
- (G73.6) Metabolic myopathies result from defects in biochemical metabolism that primarily affect muscle
(G73.6/E74.0) Glycogen storage diseases may affect muscle
(G73.6/E75) Lipid storage disorder
- (G73.6/E74.0) Glycogen storage diseases may affect muscle
- (G73.6/E75) Lipid storage disorder
- (M33.0-M33.1) Dermatomyositis, (M33.2) polymyositis, inclusion body myositis, and related myopathies
- (M61) Myositis ossificans
- (M62.89) Rhabdomyolysis and (R82.1) myoglobinurias
- Common muscle (R25.2) cramps and (M25.6) stiffness, and (R29.0) tetany

# Causes

## Life Threatening Causes
- Amyloidosis
- Malignancy
- Osteomalacia
- Polymyositis
- Sarcoidosis

## Common Causes
- Aconitase deficiency
- Becker muscular dystrophy
- Brody myopathy
- Caveolin-3 related distal myopathy
- Congenital muscular dystrophy
- Desmin-related myopathy
- Distal myopathy 2
- Duchenne muscular dystrophy
- Emery-dreifuss muscular dystrophy
- Familial partial lipodystrophy type 2
- Laing distal myopathy
- Lama2-related muscular dystrophy
- Limb girdle muscular dystrophy
- Mitochondrial myopathy
- Mitochondrial trifunctional protein deficiency
- Miyoshi muscular dystrophy 2
- Muscular dystrophy
- Myoneurogastrointestinal encephalopathy syndrome
- Myosin storage myopathy
- Myotonia congenita
- Myotonic dystrophy
- Nonaka myopathy
- Osteomalacia
- Polymyositis
- Rigid spine muscular dystrophy
- Rippling muscle disease
- Salih myopathy
- Spheroid body myopathy
- Tubular aggregate myopathy
- Ullrich congenital muscular dystrophy
- Welander muscular dystrophy

## Causes by Organ System

## Causes in Alphabetical Order
- Aconitase deficiency
- Addison's disease
- Adenosine monophosphate deaminase deficiency
- Alcoholism
- Aldolase a deficiency
- Alpha-mannosidase deficiency
- Amish nemaline myopathy
- Amyloidosis
- Anoctaminopathy
- Arnold stickler bourne syndrome
- Arthrogryposis
- Atorvastatin
- Barth syndrome
- Becker muscular dystrophy
- Bethlem myopathy
- Bezafibrate
- Borud syndrome
- Brody myopathy
- Brown recluse spider poisoning
- Calpainopathy
- Carey-fineman-ziter syndrome
- Carnitine deficiency
- Carnitine palmitoyltransferase 2 deficiency
- Caveolin-3 related distal myopathy
- Chanarin-dorfman disease
- Chloroquine
- Christian syndrome 1
- Chronic hypokalemia
- Clevudine
- Colchicine
- Congenital muscular dystrophy
- Cushing's disease
- Cytochrome-c oxidase deficiency
- Dermatomyositis
- Desmin-related myopathy
- Diabetes
- Distal myopathy 2
- Duchenne muscular dystrophy
- Efavirenz
- Emery-dreifuss muscular dystrophy
- Ethanol
- Familial partial lipodystrophy type 2
- Forbes disease
- Freeman-sheldon syndrome
- Fukuyama congenital muscular dystrophy
- Gigantism
- Glutaric acidemia type 2
- Glycerol kinase deficiency
- Glycogen branching deficiency
- Glycogen storage diseases
- Glycogenosis
- Hereditary fibrosing poikiloderma
- Hiv-1 disease
- Hypercalcemia
- Hyperkalemia
- Hypermagnesemia
- Hyperparathyroidism
- Hyperthyroidism
- Hypocalcaemia
- Hypokalaemia
- Hyponatremia
- Hypothyroidism
- Kearns-sayre syndrome
- Lactate dehydrogenase deficiency
- Laing distal myopathy
- Lama2-related muscular dystrophy
- Limb girdle muscular dystrophy
- Long chain hydroxyacyl-coa dehydrogenase deficiency
- Lundberg ii syndrome
- Malignancy
- Malignant hyperthermia
- Marinesco-sjogren-garland syndrome
- Melas
- Merrf
- Mitochondrial myopathy
- Mitochondrial trifunctional protein deficiency
- Miyoshi muscular dystrophy 2
- Molybdenum cofactor deficiency
- Muscle-eye-brain disease
- Muscular dystrophy
- Myoneurogastrointestinal encephalopathy syndrome
- Myosin storage myopathy
- Myotonia congenita
- Myotonic dystrophy
- Neutral lipid storage disease
- Niacin
- Nonaka myopathy
- Osteomalacia
- Periodic paralysis
- Phencyclidine
- Phosphogylcerate mutase 2 deficiency
- Plasma membrane carnitine transporter deficiency
- Polymyositis
- Polyneuropathy
- Pork tapeworm
- Pravastatin
- Prednisolone
- Progressive external ophthalmoplegia
- Proximal renal tubular acidosis
- Rickets
- Rigid spine muscular dystrophy
- Rippling muscle disease
- Rosuvastatin
- Salih myopathy
- Sarcoidosis
- Short chain acyl-coa dehydrogenase deficiency
- Simvastatin
- Spheroid body myopathy
- Steroids
- Stormorken syndrome
- Subacute necrotising encephalomyelopathy
- Tel hashomer camptodactyly syndrome
- Telbivudine
- Thyroid eye disease
- Tk2-related mitochondrial dna depletion syndrome
- Triosephosphate isomerase deficiency
- Tubular aggregate myopathy
- Type iii glycogen storage disease
- Udd-markesbery tardive muscular dystrophy
- Ullrich congenital muscular dystrophy
- Walker-warburg syndrome
- Welander muscular dystrophy
- Wieacker-wolff syndrome
- Woods black norbury syndrome
- Xanthine oxidase deficiency
- Zidovudine

# Differential Diagnosis of Muscle Weakness
To review the differential diagnosis of Proximal muscle weakness, click here.
To review the differential diagnosis of Distal muscle weakness, click here.
To review the differential diagnosis of inflammatory myopathy, click here.
To review the differential diagnosis of Muscle weakness and Fever, click here.
To review the differential diagnosis of Muscle weakness and Myalgia, click here.
To review the differential diagnosis of Muscle weakness and Gait abnormality, click here.
To review the differential diagnosis of Muscle weakness and Neuropathy, click here.
To review the differential diagnosis of Muscle weakness and stiffness, click here.
To review the differential diagnosis of Muscle weakness and Myoglobinuria, click here.
To review the differential diagnosis of Muscle weakness and Atrophy, click here.

# Treatment
Because different types of myopathies are caused by many different pathways, there is no single treatment for myopathy. Treatments range from treatment of the symptoms to very specific cause-targeting treatments. Drug therapy, physical therapy, bracing for support, surgery, and even acupuncture are current treatments for a variety of myopathies.

# Prognosis
The prognosis for individuals with a myopathy varies. Some individuals have a normal life span and little or no disability. For others, however, the disorder may be progressive, severely disabling, life-threatening, or fatal.