The lung megakaryocytes and pulmonary fibrosis in systemic sclerosis.

Systemic sclerosis (SSc) is an autoimmune connective tissue disease characterized by fibrotic changes in several organs including the lungs, skin, kidneys, muscles and the joints. The leading cause of death in SSc is pulmonary involvement consisting of pulmonary fibrosis with pulmonary hypertension. The pathogenesis of lung involvement in SSc is not yet clear though several mechanisms involving genetic, environmental, vascular, and immunological factors have been postulated. At the same time, the presence of megakaryocytes in the lungs is a less recognized concept and may also be contributing to lung fibrosis in SSc. These cells normally thought to be present only in the bone marrow have been demonstrated to be an important factor in the development of fibrosis of the bone marrow in the condition, idiopathic myelofibrosis. The article describes available evidence for the presence of lung megakaryocytes and hypothesizes that these cells are responsible for the development of pulmonary fibrosis in SSc based on the myelofibrosis model.