Which disorder is characterized by a progressive loss of myelin in the central nervous system?

Multiple sclerosis is characterized by a progressive loss of myelin in the central nervous system. In this disorder, the immune system mistakenly attacks the myelin sheath that insulates nerve fibers, leading to a range of neurological symptoms. This demyelination disrupts normal nerve conduction and can affect various parts of the central nervous system, resulting in symptoms such as weakness, coordination problems, sensory disturbances, and cognitive changes.

The progressive nature of this loss can lead to significant disability over time, as the damage accumulates and the ability for the nervous system to repair itself diminishes. This disorder typically presents in young adults and can have both relapsing and progressive courses.

The other conditions mentioned have different pathophysiologies and target different aspects of the nervous system. For instance, Guillain-Barré syndrome primarily affects the peripheral nervous system rather than the central nervous system. Neuromyelitis optica can also involve myelin loss but is distinct from multiple sclerosis, as it has a different underlying mechanism and tends to affect the optic nerves and spinal cord more severely. Huntington's disease is a genetic disorder that leads to progressive degeneration of specific brain areas but does not primarily involve myelin loss.