Which is the most common and severe form of muscular dystrophy?

• A. Becker Muscular Dystrophy
• B. Duchenne Muscular Dystrophy (DMD)
• C. Limb-Girdle Muscular Dystrophy
• D. Myotonic Dystrophy

Answer: (B)

Duchenne muscular dystrophy is the most common muscular dystrophy in children and the most severe form because it causes early, rapid muscle weakness from the start of motor development. It results from mutations in the DMD gene that produces dystrophin, a protein that stabilizes muscle cell membranes during contraction. Without dystrophin, muscles (especially the proximal muscles of the hips and shoulders) deteriorate quickly. Typical signs include delayed walking, frequent falls, a Gowers’ sign when getting up from the floor, and calves that look enlarged but are weak (pseudohypertrophy). The disease progresses despite support, with loss of independent walking in early adolescence and serious heart and lung complications that shorten lifespan.

Becker muscular dystrophy also involves dystrophin but with some functional dystrophin remaining, so weakness progresses more slowly and onset is later, making it less severe overall. Limb-girdle muscular dystrophies comprise many forms affecting different muscles and can vary widely in age of onset and progression, so they aren’t the single most common or most severe form. Myotonic dystrophy has distinct features like myotonia and multisystem involvement and is not the typical severe childhood form.