JAK2 and myeloproliferative neoplasm: These variants include JAK2 V617F, JAK2 exon 12/13, calreticulin (CALR), and MPL W51F. Although these variants are somatic mutations that are not inherited in the great majority of MPN patients, they can appear as early in life as at 33 weeks of gestation and lie dormant for decades, if not for a lifetime [1].