The amount of fibronectin expression was correlated to reduced hemoglobin levels in patients with MPN in the absence of reticulin fibrosis.81 In another study, patients with PMF were found to have elevated mesenchymal stromal cell expression of fibronectin compared to patients with ET and controls.82 One study showed that fibronectin can activate monocytes in patients with MF via increased monocytic production of substance P, a proinflammatory cytokine.83 The gene discussed is FN1; the disease is essential thrombocythemia.