A patient with therapy-resistant and progressive systemic sclerosis (SSc) with pulmonary involvement who was treated with imatinib mesylate is described herein. Prior to treatment, pulmonary fibroblasts obtained from the patient were cultured and incubated with imatinib mesylate. Preincubation of the fibroblasts for 16 hours with 2.5 microg/ml imatinib mesylate efficiently abrogated platelet-derived growth factor BB-induced fibroblast proliferation. Furthermore, transforming growth factor beta1-induced type I collagen gene transcription was blocked. During treatment, the patient's pulmonary involvement stabilized and her skin tightness improved. To our knowledge, this is the first report of a patient with therapy-refractory SSc responding to treatment with imatinib mesylate.