A 24 yr old white female presented with dyspnoea, orthopnoea, paroxysmal nocturnal dyspnoea, cough and fatigue. Transthoracic echocardiography revealed a sinus venosus atrial septal defect (ASD). Right heart catheterization confirmed severe pulmonary hypertension (80/37 mmHg). A chest radiograph showed enlarged pulmonary arteries with peripheral pruning. Surgical repair of the ASD and lung biopsy were performed. Two days later, she developed right heart failure and was treated with inhaled nitric oxide and then a calcium channel blocker. She failed to improve and was readmitted three months later with severe right heart failure and progressive dyspnoea. While waiting for lung transplantation, she developed haematochezia and died. Light microscopy of lung biopsy and autopsy tissue revealed the structural changes of pulmonary hypertension and focal increases in congested pulmonary capillaries consistent with the diagnosis of pulmonary capillary haemangiomatosis. Quantitative analysis demonstrated that the pathological changes were rapidly progressive.