A pathogenic role for developing bone marrow fibrosis is suggested for transforming-growth-factor beta (TGF-β), platelet-derived-growth factor (PDGF), basis-fibroblast-growth factor (BFGF), and vascular-endothelial-growth factor (VEGF) [2,5,6]. Here, TGFB1 is linked to primary myelofibrosis.