Final answer:
The ability to walk in someone with myelodysplasia (DMD) is determined by the progression of muscle weakness in the lower limbs, which worsens over time. Difficulty with balance and motion manifest in early childhood, leading to the need for braces and potential loss of walking ability by age 12.
Step-by-step explanation:
The key determining factor for whether a person with myelodysplasia, likely meant as Duchenne Muscular Dystrophy (DMD), is able to walk is the progression of muscle weakness. DMD is a genetic disorder that primarily affects males and is caused by mutations in the dystrophin gene. This condition first becomes apparent with symptoms such as difficulty with balance and motion, and difficulty walking often becomes noticeable when a child starts to walk.
As the disorder progresses, muscle weakness affects the lower limbs, making it increasingly difficult to walk. By the age of 10, many patients require braces and may lose the ability to walk entirely by around age 12. The severity of muscle deterioration in the lower extremities is the critical factor in walking ability. Over time, DMD affects not just mobility but also the muscles responsible for breathing and circulation, leading to life-threatening complications.