A case of BCR-ABL-Negative myeloproliferative neoplasm presenting with basophilia

The presence of basophilia on peripheral smear along with neutrophilic leukocytosis is the key differentiating point between chronic myeloid leukemia (CML) and all other myeloproliferative neoplasms (MPNs). However, this is not the case always. After getting negative results for the common transcripts (major, minor, and micro) of the BCR-ABL fusion gene in a case presenting with anemia, mild leukocytosis, basophilia, and eosinophilia; the patient was investigated thoroughly for other MPN-associated mutations. The results obtained were positive for the Jak2 V167 mutation. It is very unusual to find basophilia in BCR-ABL negative MPNs. This implies that any case presenting with basophilia and carrying a suspicion of MPN should be exhaustively tested for all possible mutations (JAK 2 exon 14, exon 12, CALR, MPL, CSF3R, PDGFRa, and FIPIL1) if the results for BCR-ABL are negative. Atypical CML should be the last diagnosis based on the exclusion of other MPNs.