Causes of Devic’s Disease

Virus

Devic’s disease is a type of autoimmune disorder which means that it is caused by a malfunction of the immune system. The latter plays the key role in protection of the body from infectious agents including bacteria, viruses, fungi and parasites. But in people with an autoimmune disorder, the immune system does not only attack the harmful invaders. For yet unknown reason, it identifies the body’s own cells as harmful invaders and triggers a release of antibodies to destroy those invaders which, however, play the key role in the bodily functions.

In people with Devic’s disease, the immune system attacks myelin in the optic nerve or/and spinal cord, and causes damage to this tissue which surrounds the nerves and plays the key role in transmission of the nerve signals. The damage results in transverse myelitis or/and optic neuritis which can cause disabling consequences including permanent loss of sight and paralysis in one or both legs. However, the immune system does not attack myelin all the time. Some people have the so-called monophasic Devic’s disease and experience only one attack. The majority, however, has relapses every few months or years.

Why the immune system perceives myelin as a threat which needs to be destroyed remains unclear. So far the scientists have managed to discover that the attacks are not caused by T cells which are normally released by the immune system to eliminate the harmful invader but a type of antibodies called NMO-IgG. These antibodies are known to target a protein known as aquaporin 4, however, the role of NMO-IgG in the destruction of myelin remains unknown.

Genetic factors have not been linked to the disorder so far despite the fact that Devic’s disease is more common in people of African and Asian descent than in other people which suggests that hereditary may play a role in the disease. The condition is also more common in women than men, while most patients are young adults. But since epidemiology of Devic’s disease is not established, it is difficult to draw any conclusions in relation to hereditary, gender and age.

Some scientists believe that the disease may be related to infectious agents and some environmental factors because about one half of all attacks are preceded by symptoms which indicate an infection. Some of the suspected triggers include most viral infections and tuberculosis. But at the moment of writing, there are no firm evidence to support this theory.

As long as the causes of Devic’s disease or factors which trigger the immune system to attack myelin remain unknown, patients remain dependent on treatments which only help relieve the symptoms and reduce the frequency of the attacks. This slows down damage to myelin but it does not prevent it. As a result, about 50 percent of Devic’s disease sufferers with relapses develop paralysis or/and blindness within a period of 5 years after the onset of symptoms.