Which disease is characterized by the deterioration of the myelin sheath in the central nervous system?

Multiple sclerosis is indeed characterized by the deterioration of the myelin sheath in the central nervous system. This autoimmune disorder leads to the immune system mistakenly attacking the myelin, which is the protective covering that surrounds nerve fibers. As the myelin deteriorates, it disrupts the communication between the brain and the rest of the body, leading to a wide range of neurological symptoms such as muscle weakness, coordination problems, and sensory disturbances.

In contrast, the other conditions listed affect different aspects of muscle function and motor control. For instance, amyotrophic lateral sclerosis primarily affects motor neurons rather than the myelin. Duchenne muscular dystrophy is a genetic disorder affecting muscle fibers directly through a deficiency in dystrophin, leading to muscle degeneration. Myasthenia gravis is an autoimmune condition that disrupts communication between nerves and muscles at the neuromuscular junction rather than affecting the myelin sheath. Thus, the unique characteristic of multiple sclerosis—involving the degeneration of the myelin sheath—distinguishes it as the correct answer to the question.