|Genetic and environmental factors|
In around 10% of cases, ALS has a genetic cause i.e. is due to a mistake in a gene which can be passed from parent to child. In this case, the disease is known as familial ALS (F-ALS). Only a few genes are known to be directly involved in developing F-ALS. One of these is SOD1, which causes around 10-20% of F-ALS. The recently discovered changes in a gene for TDP-43 are far less frequent. However, in 90% of cases, the disease has no known cause and is not passed on to children. This is known as sporadic ALS. We do not yet know what causes sporadic ALS, but it is likely that subtle alterations in a number of genes may combine to increase an individual’s susceptibility to develop ALS.
Researchers believe that discovering the genetic causes of familial ALS will lead to a better understanding of what is going wrong in the more common, sporadic forms of ALS, since both forms of ALS are clinically indistinguishable and the mechanisms underlying both types of disease are likely to be similar as well. Hunting for gene variations in ALS is currently underway in a number of laboratories worldwide since understanding the consequences of these gene variations might eventually lead to new treatment strategies.
Lifestyle and environment :
Exposure to environmental factors might contribute to the development of ALS. Epidemiological research has identified possible links with a number of factors including: prior exposure to mechanical and/or electrical trauma, military service, high levels of exercise, agricultural chemicals and a variety of heavy metals. It is not known how environmental and lifestyle factors could increase the risk of ALS, but one possible explanation is that they have a cumulative effect in weakening motoneurons, making them more susceptible to the cellular mechanisms listed above that result in their degeneration.
Some factors may be protective and for example studies examining the impact of diet on the risk of developing ALS, have suggested that a diet of high vitamin E and polyunsaturated fat may reduce the risk of developing the disease. However, there is no firm data to support this possibility