Myeloproliferative neoplasms (MPNs) are a group of clonal disorders characterized by hyperproliferation of hematologic cell lines and have been associated with tyrosine kinase JAK2-V617F mutations. Secondary acute myeloid leukemia (sAML) is a known complication of JAK2-V617F+ MPNs and bears a poor prognosis. Although the evolution of a JAK2-V617F+ MPN to a mixed-lineage leukemia has been reported in the pediatric population, no evolutions into sAML have been described. We present a case of a one-year-old girl diagnosed with JAK2-V617F+ MPN with evolution into sAML. Despite initial morphologic remission, she eventually relapsed and succumbed to her disease. 1. Introduction Myeloproliferative neoplasms (MPNs) are a heterogeneous group of disorders manifested by increased hematopoiesis and proliferation of one or more of the hematologic cell lines. A mutation in the tyrosine kinase JAK 2 (JAK2-V617F) is frequently encountered in patients with MPNs [1]. Adults with JAK2-V617F+ MPNs can evolve into acute myeloid leukemia (AML). Evolution into AML from a known MPN is included in the category of secondary AML (sAML). Conversely, the JAK2-V617F mutation is more common in sAML than de novo AML [2–6]. Secondary AMLs evolving from JAK2-V617F+ MPNs bear a poor prognosis since first complete remission (CR) is difficult to obtain; even matched sibling donor hematopoietic stem cell transplant (HSCT) recipients have poor outcomes [4, 7–9]. JAK2-V617F mutations have been described in pediatric patients with MPNs, but the evolution into sAML has not [10]. We describe a case of a one-year-old girl with a JAK2-V617F+ MPN that evolved into sAML. 2. Case Report An 1-year old female presented with a two-month history of fever, fussiness, and refusal to bear weight. Significant physical findings included a one centimeter, freely mobile, nodular mass under her right eyebrow, diffuse lymphadenopathy, and absence of organomegaly. Initial hematologic evaluation revealed a white blood cell count (WBC) of /L, hemoglobin of 9.6？g/dL, and a platelet count of /L. The WBC differential demonstrated a left shift with 2% peripheral blasts. Bone marrow evaluation on hospital day (HD) three was morphologically concerning for myelodysplastic syndrome revealing hypercellularity (Figure 1(a)) with blasts constituting 4% of marrow cells (Figure 1(b)). Cytogenetics revealed 46,XX,dup(8)(q21.3q23), add (11)(p13),del (13)(q12q14),add (18)(p11.2) /46,sl,add(X)(q26),add(3)(p25),add(9)(q32),-del (13), inv (15)(q15sq26.1),+18,-add (18),+mar .ish add (11)(MLL+), which, although complex, identified no
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