<s>[INST] context: Although a difficult diagnosis to make, pulmonary arterial hypertension (PAH) is the most likely diagnosis in this young woman who has used appetite suppressants. Pulmonary arterial hypertension (also known as primary pulmonary hypertension) has been associated with fenfluramine-type appetite suppressants. The predominant symptom is dyspnea, which is usually not apparent until the disease has advanced. When physical findings, chest x-ray, or echocardiography suggest pulmonary hypertension, recurrent pulmonary emboli must be ruled out. In this case, a normal perfusion lung scan makes pulmonary angiography unnecessary. Right-to-left cardiac shunts cause hypoxia (oxygen desaturation) that characteristically does not improve with oxygen supplementation. Restrictive lung disease should be ruled out with pulmonary function testing but is unlikely with a normal chest x-ray. An echocardiogram will show right ventricular enlargement and a reduction in the left ventricle size consistent with right ventricular pressure overload. Left ventricular dysfunction can cause pulmonary edema but not pulmonary hypertension. [/INST] question: A 35-year-old woman complains of slowly progressive dyspnea. Her history is otherwise negative, and there is no cough, sputum production, pleuritic chest pain, or thrombophlebitis. She has taken appetite suppressants at different times. Physical examination reveals jugular venous distention, a palpable right ventricular lift, and a loud P2 heart sound. Chest x-ray shows clear lung fields. Oxygen saturation is 94%. ECG shows right axis deviation. A perfusion lung scan is normal, with no segmental deficits. Which of the following is the most likely diagnosis? | options: A: Pulmonary arterial hypertension B: Recurrent pulmonary emboli C: Right-to-left cardiac shunt D: Interstitial lung disease | answer: A </s>