Is Motor Neurone Disease Hereditary?

Amyotrophic lateral sclerosis (ALS) or motor neurone disease occurs when special nerve cells in your brain and spinal cord do not work properly and degenerate. These motor neurons are important in muscle activity because they control your ability to walk, grip, speak, swallow and breathe. As neuro degeneration progresses, you will find it increasingly difficult to do these otherwise simple activities, and eventually you may be unable to do them at all.

Is Motor Neurone Disease Hereditary?

Possible, but rare. It may be inherited, but in most cases, there is no familial or genetic predisposition to the disease.

In most cases, people who have motor neurone disease (MND) or ALS do not have a family history of the disease. Only about 10% of patients who have it may have inherited it from another family member. In 20% of these cases, the cause is a gene mutation, which may be revealed through genetic testing.

MND Where There Is a Family History

In patients who are known to have inherited the disorder, very few are aware that a close member of their family ever had the disease. These may include parents, siblings, grandparents, uncles, aunts or cousins with MND or a related condition called FTD (frontotemporal dementia). Familial MND has a genetic component, but other factors, such as aging, may contribute before the manifestations of the disease begin. In many cases, however, it is difficult to determine whether the problem was inherited because of other factors like adoption or other similar medical problems in the family, which are not brought into the open.

Genetic Testing

Is motor neurone disease hereditary? One way to find out is through genetic testing in patients who have family members with the same condition. The presence of genes called C9orf72 and SOD1 can give a clue to whether a patient has the genetic predisposition for the disorder. However, there are other genes that have also been associated with MND, and routine testing for these is not available. Patients with a defective C9orf72 gene are more likely to have relatives with dementia and are also more likely to pass it on to their children. Their children may live long, however, and die of other causes such as cancer or heart disease before they manifest FTD or MND. Therefore, routine testing for family members without symptoms of the disease is not recommended.

Is motor neurone disease hereditary? People who have a family member with the disease and are planning to have children might want their embryos to get screened for faulty genes. This is quite unusual and so a genetic counselor must be consulted.

Genetic testing, therefore, is generally recommended only for people who have symptoms of FTD or MND, who have a high probability of having a positive result, based on the opinion of their neurologist and genetic counselor.

Possible Causes of MND

Aside from genetic factors, little is known about the causes of MND. It may due to interplay between genetic and environmental factors such as exposure to toxic chemicals, as well as injuries, smoking habits, military service or increased levels of exercise. However, research has not found conclusive evidence to support any of these possible causes. It is possible that various factors are involved, rather than just a single cause, which could trigger the development of the disease.

Internal Problems

It is still not clear why motor neurones degenerate and lose function. Experts believe that it may be a combination of various factors that may affect either these motor neurones or other nerve cells supporting them. Knowing these factors may help you better understand the question of "Is motor neurone disease hereditary?"

Here are some of the possible causes of MND:

  • Aggregatesand RNA processing

Studies show that aggregates orabnormal protein clumps develop inside the motor neurons of people who have MND. These may cause disruption of the normal function of motor neurones or become markers that the cells are under strain. They may also affect the correct processing of the cells’ genetic instructions through the RNA molecules.

  • Disruption of cell transport

Research suggests that the transport systems responsible for moving nutrients and waste products in and out of the cells may be disrupted in people who have MND. This causes toxic wastes to build up in the cells during normal cellular activity. It has also been found that patients who have MND are deficient in antioxidants, which helps the body get rid of the toxic wastes. However, there is no evidence that poor dietary intake is related to this process.

  • Glial cell problems

Glial cells support the motor neurones by providing them with nourishment and helping relay information nerve cell to nerve cell. Glial cell problems can cause motor neurones to stop receiving support and the nutrition they need for normal functioning.

  • Sensitivity to glutamate

Research shows that people with MND have motor neurones that develop an increased sensitivity to glutamate. Glutamate is a neurotransmitter or a special "messenger chemical" that helps pass information from cell to cell. An increase in sensitivity to this neurotransmitter is believed to cause damage to the motor neurone cells.

  • Abnormal mitochondria

Mitochondria are the powerhouse of the cells since they provide energy the cell needs to carry out normal functions. Some research shows that the presence of abnormal mitochondria in motor neurons may be linked to MND.

Environmental Factors

Possible environment risk factors that may be associated with MND include:

  • Poor diet
  • Increased stress
  • Exposure to toxic chemicals
  • Amalgam dental fillings
  • Injuries
  • Excessive exercise
  • Previous surgery
  • Chemotherapy
  • Medications for depression
  • Viruses
  • Lyme disease
  • Frequent travel
  • Muscle cramps due to sitting still for long periods
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