Motor Neuron Disease encompasses a variety of conditions, including Amyotrophic Lateral Sclerosis (ALS), Progressive Muscular Atrophy (PMA), and Primary Lateral Sclerosis (PLS). These diseases result in the gradual degeneration and death of motor neurons, leading to muscle weakness and atrophy. The exact cause of MND is still not fully understood, although it is believed to involve a combination of genetic and environmental factors.