Grey's Anatomy's Eric Dane dies after battling ALS: What causes the disease?

The popular medical series 'Grey's Anatomy' actor Eric Dane, who played the character Dr Mark Sloan, often nicknamed McSteamy by his colleagues at the Seattle Hospital, is no more. The actor lost his life ten months after he revealed that he was diagnosed with Amyotrophic Lateral Sclerosis or ALS, a neurological disorder. He was 53. After the diagnosis, the actor had revealed in various interviews the challenges of living with the progressing condition. Generally, patients with the condition lose their muscle control, and it worsens over time. Meanwhile, what causes ALS?

The exact causes
Medical experts say the exact cause of the disease has not yet been discovered. However, the Mayo Clinic says that a small number of cases are also genetic. Unfortunately, there is no cure for the condition. Interestingly, in the early stages of the disease, patients experience little pain. Even in the later stages, pain is not common. While the causes of the disease are not yet known, it has a handful of established risk factors.

ALS risk factors
1) While Eric Dane was diagnosed with it at the age of 52, the disease's risk increases with age, up to 75. It's most common among those aged 60 to 80. 
2) In certain people, the ALS risk is passed down the family tree. if a parent has ALS, there is a 50% chance that the child would inherit it.
3) The disease is diagnosed more often in men than in women
4) Certain environmental factors like military service, toxin exposures and smoking are also termed risk factors of ALS

Common ALS symptoms
1) Weakness and clumsiness
2) Changes in behaviour and thinking
3) Emotional instability
4) Difficulty walking
5) Tendency to trip, fall
6) Speech issues
7) Difficulty swallowing
8) Muscle cramps
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