Multiple sclerosis (MS) creeps into someone's life as a series of small, almost ignorable annoyances: a bit of numbness or tingling, fatigue or some troubles with vision. As the disease progresses on its course of destroying the myelin sheaths that protect the nerves, the body and sometimes the mind as well, it enters a long slide into dysfunction. That MS tends to strike in young adulthood renders the debilitation all the more tragic.

The disease has proved stubbornly resistant to medical intervention, in part because it remains so poorly understood — we do not even know how it begins. The reigning theory is that MS is an autoimmune disorder in which the white blood cells attack the body's myelin. But what sets the immune system off? Efforts to find the trigger have failed. This gap has given strength to an alternative hypothesis: that MS starts in the neurons of the brain, and triggers an immune response that spreads out into the peripheral blood and cerebrospinal fluid. As 'The X factor' notes, “The harder researchers look at what triggers MS, the less they understand about its origin and progression” (see The X factor).

Other aspects of MS are beginning to yield their secrets, however. The genetics of MS are becoming clearer, for example, thanks to recent studies that have identified about 100 variants associated with the disease (see A complex code). Although a cure is not yet in sight, several drugs in the pipeline offer a tantalizing promise of effectiveness. These include several that can be taken orally — a big improvement over regular painful injections. But it is an intravenous drug, alemtuzumab, that holds the most hope: in preliminary human tests it seems to not only halt the progression of MS, but also to promote myelin repair, possibly reversing the disease (see An injection of hope). Unfortunately, such drugs work only on the more common form of the disease, known as relapsing–remitting MS. Those afflicted with the progressive form, which is characterized by a steady physical decline, have little relief in sight (see The treatment gap).

It is no surprise that some patients, faced with such a grim prognosis, venture outside the realm of conventional medicine. The most promising of these off-beat treatments involves parasitic worms known as helminths, which excrete immunomodulatory agents shown in preliminary studies to suppress the symptoms of MS (see Desperate measures).

As the articles in this Outlook document, MS research is a multidisciplinary, multifaceted endeavour that is making steady progress towards better understanding, and ultimately treatment, of this disease.