Which condition should be considered in patients with weakness, fatigue, a myopathic waddling gait, muscle stiffness, and delayed grip relaxation?

The symptoms described—weakness, fatigue, a myopathic waddling gait, muscle stiffness, and delayed grip relaxation—are characteristic of myotonic dystrophy. Myotonic dystrophy is a neuromuscular disorder that is known for muscle weakness and myotonia, which is the delayed relaxation of muscles after contraction, particularly noticeable with grip strength. The waddling gait results from weakness in the proximal muscle groups, and the muscle stiffness can contribute to difficulties in mobility.

In myotonic dystrophy, the delayed grip relaxation is particularly telling, as this can help differentiate it from other causes of muscle weakness. The combination of progressive weakness, characteristic gait, and symptoms such as myotonia aligns well with this condition, making it the most fitting answer in this case.

Other conditions may present with weakness and fatigue, but they typically do not encompass all the specific symptoms listed here in the same way as myotonic dystrophy does.