Pulmonary fibrosis (PF) is a rare disease that develops as the final stage of scarring after a series of episodes of lung injury. PF is idiopathic in most cases (60%), though the exact rate varies from series to series. Childhood PF, which is even rarer than the adult form, is usually diagnosed when the patient is less than five years old. Some cases are familial. We report the case of a 14-year-old girl admitted with a three-year history of dry cough and increasing dyspnea that eventually appeared even with moderate effort. Pulmonary biopsy by mini-thoracotomy showed diffuse fibrosis of unknown cause. She died four years after diagnosis. The patient's age, the rapid course of disease, and the final outcome are all unusual features of this case.