The constitutively active JAK2 mutant V617F is found in many patients with myeloproliferative diseases (Levine and Gilliland, 2007), and constitutively phosphorylated STAT3 is found in many solid tumours and haematopoietic malignancies (Lim and Cao, 2006). The gene discussed is JAK2; the disease is myeloproliferative disorder.