In cases of Duchenne muscular dystrophy, which specific muscle weakness is typically observed first?

In Duchenne muscular dystrophy (DMD), proximal muscle weakness is typically the first observable clinical manifestation. DMD primarily affects young boys and results from a mutation in the dystrophin gene, leading to progressive muscle degeneration. The disease is characterized by weakness starting in the proximal muscles, particularly those of the pelvis and shoulders.

This proximal weakness manifests as difficulty in activities such as climbing stairs, running, or getting up from the floor, which is often noticeable when the child has difficulty standing up from a seated position (a sign known as "Gower's sign"). As the disease progresses, weakness can spread to other muscle groups, but proximal muscles are consistently affected early on.

Other options, such as weakness in distal arm muscles or facial muscles, are not the initial features of DMD. Distal muscle weakness tends to develop later in the disease, while facial muscle weakness is typically associated with other neuromuscular conditions rather than DMD specifically. Core muscle weakness may occur as the disease progresses but is not the first notable weakness in DMD. Therefore, recognizing proximal muscle weakness as the initial symptom is vital for early diagnosis and intervention.