Multiple sclerosis (MS) is a chronic disorder affecting white matter (myelin) of the Central Nervous System (CNS). During the disease, the damage and the myelin loss occur in different brain areas (namely “multiple”). These events lead to newly forming lesions which evolve from an initially inflammatory phase to a chronic phase, in which they look like scars (the disease name “sclerosis” refers to scars). In the world, 1.3 million people are affected by MS, including about 60.000 in Italy. The disease distribution is not uniform: MS is most common in people who live farther from the equator in temperate climates, particularly northern Europe, United States, whereas it is less common in areas near the equator. MS is usually diagnosed between the ages of 20 and 40 and it is twice as common in women as in men. MS patients display different symptoms due to the location of the lesions within the central nervous systems. The most common are: 1) visual problems (sudden vision loss, double vision, uncontrolled eye movements) 2) sensory disturbances (tingling, numbness in arms and legs,  loss of sensitivity to touch, difficulty with feeling of hot and cold) 3) tiredness and weakness (difficulty with performing activities of daily life, loss of muscle tone). Approximately 90% of cases are initially diagnosed with “relapsing-remitting (RR)” form, characterized by attacks  and remissions. The attacks often include one or more symptoms described above, of variable severity. Symptoms usually last for at least one day and generally disappear until a complete recovery (remission phase). In the course of time, RR form can convert to “secondary progressive” MS (40% within 10 years and 25% within 25 years), characterized by few relapses and by a gradual but progressive increase of disability.  There is also another form of MS which progresses from the outset (“primary progressive”),  worse than the RR form, that occurs in approximately 10% of patients and it is characterized by a general absence of attacks and a progressive worsening of disability. It’s believed that the disease is caused by an abnormal activation of immune cells, that are wrongly activated in the periphery, they move in the brain where they attack myelin, as if it were an undesirable foreign body. This triggers the secretion of inflammatory molecules which thus damage the myelin. The body is able to recover for some time, but when the myelin is not reformed, the neuronal cells begin to die, process that appears with progressive disability. The disease is very heterogeneous and presents benign cases, in which the frequency of attacks is low and the disability is minimal and cases in which the progression is more rapid and severe.