患儿，男，８岁，于４岁时其家长发现双下肢行走无力，后逐渐加重，至６岁时发现腓骨肌萎缩，双足呈下垂状，弓形、内翻、呈跨步状态，需扶起走路，于７岁时发现双上肢乏力，手指不能伸直，否认有家族史。查体：意识清，精神不振，智力正常。胸腹部检查未见异常。双上肢肌力Ⅳ? Children, male, 8 years old, at 4 years of age, their parents found that their lower extremities were walking weak and gradually worsened. By the age of 6, they found atrophy of the phonydiscus muscle, drooping sagittal legs, bowing, pronation and stride. Fuqi walk, at the age of 7 found that upper extremity fatigue, fingers can not be straight, denied a family history. Examination: Consciousness, lack of energy, mental normal. No abnormal chest and abdomen examination. Upper limb muscle strength Ⅳ?