Sir,The report on isolated large vessel pulmonary vasculitis and chronic obstruction of the pulmonary arteries by Hagan et al. is very interesting[1]. Hagan et al. noted the usefulness of positron emission tomography and magnetic resonance imaging. It is agreeable for the usefulness of the new imaging technology, but there are some limitations in using. First, the cost of the test and the availability of the analyzer are the main obstacles. The careful history taking and examination might still be helpful in the setting limited resources.[2] Second, the practitioners have to keep in mind for the differential diagnosis.[2] In the present case, the cases were firstly misdiagnosed to be chronic thromboembolic pulmonary hypertension.