In addition, CALR mutations have been detected rarely in chronic myelomonocytic leukaemia (CMML)1, myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN)3, and a few myelodysplastic syndrome (MDS) patients, mainly with refractory anaemia with ring sideroblasts, refractory anaemia, and refractory anaemia with excess blasts4. The gene discussed is CALR; the disease is myelodysplastic syndrome with single lineage dysplasia.