Abstract
BACKGROUND: Chronic neutrophilic leukemia (CNL) is an extremely rare myeloproliferative neoplasm (MPN). Due to the difficulty in its diagnosis, the diagnostic criterion was just recently revised in 2016. CNL is defined as: A clonal disorder with sustained primary neutrophilia, with normal neutrophil maturation, that does not meet other MPN criteria, as well as no identifiable mutations of the PDGFRA, PDGFRB or FGFR1 or PCM1-JAK2 genes, and, either, the presence of a CSF3R mutation, or if absent, the presence of sustained neutrophilia (> 3 months), splenomegaly and no other identifiable cause of reactive neutrophilia including the absence of a plasma cell neoplasm, or, if present, demonstration of myeloid cell clonality by cytogenetics. Only about 200 cases have been reported. CASE PRESENTATION: We report a 61-year-old Caucasian male patient who initially presented with unexplained leukocytosis. An outpatient work-up was planned to rule out a myeloproliferative disorder but the patient was acutely admitted for MRSA septic shock. The patient was stabilized prior bone marrow work-up and was then diagnosed with an atypical type of CNL (JAK2 positive, CSF3R negative). The patient refused further treatment due to social circumstances and requested palliative care instead. CONCLUSION: This case aims to present atypical findings of an extremely rare MPN. Even though a recent revision has been made to help in its diagnosis, atypical findings must still be considered. This, in turn, will help to further improve the current CNL diagnostic criteria.