A 9-year-old girl with a history of xerostomia and recurrent bilateral parotid gland enlargement presented with purpura of the lower limbs and exertional dyspnea. She had hyperglobulinemia, positive ANA, SSA, and SSB and an abnormal Shirmer test leading to a diagnosis of primary Sjögren syndrome. Cardiologic and imaging investigations revealed severe isolated pulmonary hypertension and ruled out pulmonary fibrosis. Prednisolone and cyclophosphamide, together with anticoagulant and vasodilatory drugs therapy, induced a significant improvement of exertional dyspnea and lowered pulmonary artery pressure. This case and reports from the literature suggest that immune mechanisms, not just vasospasm, can be factors in some pulmonary hypertension.