ALS, also known as motor neuron disease or Lou Gehrig’s disease, is a neurodegenerative disorder that affects nerve cells in the peripheral and central nervous system related to muscle movement.
Currently, there is no cure for ALS. Most people with this condition will live just two to three years after symptoms appear, twenty percent of people will live five to ten years, and ten percent will survive over ten years.
In most cases, the age of onset is between forty-five to sixty-five years. As of today, there is no genetic test that can detect the disease before symptoms develop. The average prevalence of ALS worldwide is one in 50,000 people per year.
What are the symptoms?
ALS affects nerve cells that transport motor signals from the brain to the organs, causing the muscles to weaken and eventually leading to an inability to control movement.
Symptoms develop gradually, initial symptoms usually include weakness in the arms and legs, muscle twitches, cramps, slurred speech, and difficulty breathing and swallowing.
Less than five percent of people with ALS experience cognitive impairment. The most common cause of death from this disease is pneumonia and respiratory failure. Since the disease affects motor neurons, patients do not usually experience damage to their senses.
What causes ALS?
Around ten percent of ALS cases are familial (FALS). This means the disease occurs several times in the same family (such as in siblings, or parents and their children).
Around twenty percent of familial ASL cases are linked to a mutation in the gene coding superoxide dismutase 1, located on chromosome 21.
This gene mutation has an autosomal dominant hereditary pattern, there are more than one hundred different mutations that can occur in this gene.
Different types of mutations lead to different progression rates. For example, the mutation D90A leads to a disease that progresses slowly, with patients living around ten years from onset.
The large number of mutations led modern researchers to understand that environmental factors are probably much less significant in the disease’s etiology than was previously assumed.
More than just genes
Most people with ALS suffer from its non-familial form (sporadic), the cause of which is yet unknown. Several theories attempt to explain the disease onset in people with no superoxide dismutase gene mutations:
- Many cases were diagnosed among athletes who consumed high amounts of protein in their diets. It was hypothesized that over-stimulation of the cells occurred due to excessive absorption of calcium that led to death of the cells.
- Researchers found that ALS patients have high levels of the neurotransmitter glutamate in their cerebrospinal fluid compared to healthy people. This led to the development of a drug called Riluzole that acts as a glutamate release inhibitor. However, the effect of this drug on patient survival is minor.
- Other factors being researched include exposure to certain chemicals, powerful magnetic fields, electric shock, contending in sports such as wrestling, concussions, and more.