Muscle biopsy usually reveals an increased variation in the diameter of fibers and type IIb muscle fiber atrophy without muscle fiber inflammation or necrosis.

• 肌活检一般显示肌纤维直接变异的增加（这句翻译得有问题吧?）和IIb型肌纤维萎缩，但没有肌纤维炎症或坏死。