Apart from the common JAK2 V617F, MPL, and CALR mutations, several other recurrent mutations are observed in MPN but are also present in the myelodysplastic syndromes (MDS), MDS/MPN syndromes, and AML limiting their diagnostic utility but affording the potential for their use as markers of residual disease. The gene discussed is MPL; the disease is myeloproliferative neoplasm.