A male patient with advanced Duchenne muscular dystrophy (DMD) had tonic-clonic convulsion. He showed transient elevations of serum creatine kinase (CK) and plasma D-dimer. Serum CK, ordinarily 122-386 IU/l, was elevated to 9,262 IU/l, while plasma D-dimer, below 66 ng/ml in normal subjects, was at 543 ng/ml, and these levels were significantly correlated. Serum fibrin and fibrinogen degradation products levels were within a normal range. In the present case, acute muscle destruction due to tonic-clonic convulsion was considered to transiently activate a coagulation cascade. Plasma D-dimer elevation is the result of fibrin thrombus and can induce thrombosis, such as a pulmonary embolism. Thrombosis is a serious life-threatening complication of DMD, though the mechanism remains unclear. There were no thrombotic complications in the present patient, however, acute muscle destruction enhances the coagulation and fibrinolysis status in patients with advanced DMD and may be a candidate cause of thrombosis.