Thank you for the first letter commenting on our paper. In a case of pulmonary arterial hypertension (PAH) occurring in patients with ulcerative colitis (UC) under indigo naturalis treatment, PAH was associated with patients with UC after using indigo naturalis for 6 months at a dose of 2 g/d. It corresponds with the high dose (2 g/d) for 8 weeks group in our INDIGO Study,1 but she received indigo naturalis for 6 months. First, it is expected that she continued indigo naturalis as a maintenance therapy after she achieved clinical remission.