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Duchenne muscular dystrophy is a genetic disorder caused by mutations in the dystrophin gene, which leads to progressive weakness of the skeletal muscles, especially those closest to the body like the hips and legs. It affects boys far more than girls because it is inherited on the X chromosome (X-linked recessive). In early childhood, children typically show difficulties with walking, frequent falls, and trouble climbing stairs due to proximal leg and hip weakness. As the condition worsens, many will lose the ability to walk during their teens and require a wheelchair, with progressive impact on muscle strength and endurance.

The statement is the best fit because it accurately summarizes the common, defining clinical picture: it is the most common form of muscular dystrophy, it occurs predominantly in boys, and it affects walking ability. It’s not due to nutrition, it’s not typically seen only in adult women, and it is not a mild condition—it's a progressive disease that leads to significant mobility issues over time.