Is MS (Multiple Sclerosis) genetic/hereditary?

To a certain extent yes and it is important to note that just because something is an autoimmune disease does not mean that it lacks a hereditary component (actually, they often do)

Briefly, MS is generally considered as an autoimmune disease in which your bodies lymphocytes (specifically T cells) attack the coating of neuron in the nervous system. What is surprising about this is that the central nervous system (brain + spinal cord) are generally considered immune-privileged areas, meaning that immune cells do not normally have access to them. It is thought that some event causes the normal barrier between the central nervous system and the blood (which carries the lymphocytes) to become leaky, allowing the lymphocytes to enter and start attacking. Some candidates for this event are certain types of infections and simply blunt brain trauma.

However, it is clear that not everyone who has ever suffered one of the candidate infections or traumas develops MS. There is something that disposes certain individuals to the autoimmune reaction one the barrier is opened up. Normally this disposition doesn't do anything since no MS occurs until the barrier is opened up. Thus, if the barrier is never damaged, you may never develop MS even if you have the susceptibility. This is why simply having the presumed genetic disposition does not guarantee MS. In fact, the genetic risk factors are hardly ever used to determine whether someone should really be considered at risk. Instead, they are mainly used as a diagnostic tool, to help prove that an undiagnosed neurological problem in an individual with the susceptibility gene is probably MS.

From the National MS Society:

Genetic factors are thought to play a significant role in determining who develops MS. The average person in the United States has about one chance in 750 of developing MS. But close (first-degree) relatives of people with MS, such as children, siblings or non-identical twins, have a higher chance鈥攔anging from one in 100 to one in 40. The identical twin of someone with MS, who shares all the same genes, has a one in four chance of developing the disease. If genes were solely responsible for determining who gets MS, an identical twin of someone with MS would have a 100% chance of developing the disease; the fact that the risk is only 1 in 4 demonstrates that other factors, including geography, ethnicity, and the elusive infectious trigger are likely involved as well.

hth

Genetic factors may play a part in the susceptibility in certain people; but it is more generally considered an autoimmune disease.

Google: mayo clinic>>diseases>>Multiple Sclerosis