Metabolic myopathies are myopathies that result from defects in biochemical metabolism that primarily affect muscle. They are generally genetic defects that interfere with muscle's ability to create energy. At the cellular level, metabolic myopathies lack some kind of enzyme that prevent the chemical reactions necessary to create adenosine triphosphate (ATP). This prevents the muscle cells from being able to function properly and disrupts communication between joints and bones.[1] Some people with a metabolic myopathy never develop symptoms due to the body's ability to produce enough ATP through alternative pathways. In the event more ATP is needed from the affected pathway, the lack of it becomes an issue and symptoms develop. People with a metabolic myopathy often experience symptoms such as progressive muscle weakness, fatigue, pain and cramping after exercise, and considerable breakdown of muscle tissue.[1] The degree of symptoms varies greatly from person to person and is dependent on the severity of enzymatic defect. In extreme cases it can lead to the cause of Rhabdomyolysis.[2]
Contents
1Types
2Diagnosis
3Treatment
4References
5External links
Types
Metabolic myopathies are generally caused by an inherited genetic mutation. This mutation has an autosomal recessive inheritance pattern making it fairly rare to inherit, but it can also be caused by a random genetic mutation. Metabolic myopathies are named after the pathway in which the defective enzyme or a lack of enzymes is present. This causes the underproduction of adenosine triphosphate (ATP) and affects the muscles in different parts of the body.[3] The three main categories of diseases are listed below.
Glycogen storage diseases- defect in sugar metabolism
Lipid storage disorder- defect in fat processing
Mitochondrial myopathy- defect in mitochondrial enzyme
Diagnosis
The symptoms of a metabolic myopathy can be easily confused with the symptoms of another disease. In most cases, a Muscle biopsy is necessary for an accurate diagnosis of the cause of muscle weakness. A blood test can be done under normal circumstances to test for genetic differences and signs of tissue breakdown, or with an added cardio portion that can indicate if muscle breakdown is occurring. An electromyography is sometimes taken in order to rule out other disorders if the cause of fatigue is unknown.[3] Differentiating between different types of metabolic myopathies can be difficult due to the similar symptoms of each type such as Myoglobinuria and exercise intolerance. It has to be determined whether the patient has fixed or exercise induced manifestations, and if exercise related what kind of exercise, before extensive exercise related lab testing is done to determine the underlying cause. [4]
Treatment
Metabolic Myopathies have varying levels of symptoms, being most severe when developed during infancy. Those who do not develop a form of a metabolic myopathy until they are in their young adult or adult life tend to have more treatable symptoms that can be helped with a change in diet and exercise.[2] Depending on what enzyme is affected, a high-protein or low-fat diet may be recommended along with mild exercise. It is important for people with metabolic myopathies to consult with their doctors for a treatment plan in order to prevent acute muscle breakdowns while exercising that lead to the release of muscle proteins into the bloodstream that can cause kidney damage.[3]
… signs, and laboratory abnormalities resulting from a metabolic myopathy vary with the underlying defect. Most patients with a metabolic myopathy (eg, glycogen storage diseases, carnitine palmitoyltransferase …
…overview of the clinical manifestations resulting from a metabolic myopathy and the approach to the patient suspected of having a metabolic myopathy is discussed separately. The carnitine cycle shuttles …
…albumin, and uric acid; Electrocardiography; Additional testing, such as evaluation of suspected metabolic myopathy or toxicology screening for drugs of abuse, depends upon the clinical context. We make the …
…deficiency may cause exercise intolerance . The diagnostic approach to a patient with a suspected metabolic myopathy is discussed separately. Fifteen types of glycogen storage diseases (GSDs) have been identified…
…The heritable metabolic myopathies are discussed in more detail elsewhere. Carnitine palmitoyltransferase (CPT) and muscle phosphorylase deficiency are the most common metabolic myopathies . Muscle phosphorylase …
Mitochonic Acid 5 (MA-5), a Derivative of the Plant Hormone Indole-3-Acetic Acid, Improves Survival of Fibroblasts from Patients with Mitochondrial Diseases
The Tohoku Journal of Experimental Medicine 236(3), 225-232, 2015
… Mitochondrial dysfunction increases cellular oxidative stress and depletes ATP in a variety of inherited mitochondrial diseases and also in many other metabolic and neurodegenerative diseases. … Importantly, MA-5 improved the survival of fibroblasts established from patients with mitochondrial diseases under the stress-induced condition, including Leigh syndrome, MELAS (myopathy encephalopathy lactic acidosis and stroke-like episodes), Leber's hereditary optic neuropathy, and Kearns-Sayre syndrome. …
Metabolic myopathy symptoms vary among individuals. In fact, some people with the condition my live symptom-free because their cells have found a different pathway for creating energy to power muscles.
Metabolic myopathies are rare genetic diseases that cause muscle problems. Not all people with a metabolic myopathy experience the same symptoms. Despite the fact that metabolic myopathies are inherited, treatments can
Metabolic myopathies presenting with exercise intolerance, cramps, and myoglobinuria Cramps and myalgia may occur after brief exercise or after prolonged physical activity. Glycogen is the main source of energy during brief exercise, while free fatty acids are the most important source of fuel during prolonged exercise.