A 48 year-old woman presented to the emergency room with dizziness following five episodes of black stool. She had otherwise been well and denied prior episodes. Her admission labs were notable for hemoglobin of 6.2 g/dL, white blood cell count of 24,000/uL, and platelets of 1.4 million/uL. On chart review, the patient had labs drawn one month prior to admission as part of a preoperative workup for elective surgery. At that time labs had revealed platelets of 1.3 million/uL but were otherwise unremarkable. She was lost to follow-up until the current presentation. Initial impression favored reactive thrombocytosis secondary to GI bleed, and the patient was admitted for management. Her platelets peaked at 2.1 million/uL. Endoscopy found Helicobacter pylori gastritis. Peripheral blood smear was remarkable only for increased platelets, and bone marrow biopsy was most notable for erythroid and megakaryocyte hyperplasia, with only 4.5% myeloblasts on flow cytometry. Additional blood tests identified the presence of the BCR-ABL fusion gene. Subsequent cytogenetic evaluation of the bone marrow confirmed a diagnosis of chronic myelogenous leukemia (CML), with the Philadelphia translocation identified in 94.5% of cells.
Discussion:
Extreme thrombocytosis is relatively rare, and so there is a paucity of data available to guide management. The most common etiology is secondary, or “reactive” thrombocytosis, accounting for up to 72% of cases. However, as this case demonstrates, workup should also include evaluation for myeloproliferative diseases. Of these, CML is the most common etiology identified. The hallmark of CML is the reciprocal translocation between chromosomes 9 and 22 – the so-called “Philadelphia translocation,” yielding the BCR-ABL fusion gene. Bone marrow histology tends to show hypercellular marrow, typically with an increased myeloid-to-erythroid ratio, which was absent in this case. This patient instead had disproportionate erythroid hyperplasia, possibly a response to her GI bleed.
Conclusions:
This case describes an atypical presentation of CML. Ultimately, our patient presented for symptomatic GI bleed secondary to H. pylori gastritis; derangements in her blood counts were felt to be reactive. CML was not high on the differential, given her disproportionate thrombocytosis with an otherwise unremarkable peripheral smear and uncharacteristic bone marrow. Importantly, earlier labs demonstrated pre-existing thrombocytosis, suggesting a second primary process unrelated to her presenting complaints. It was this inconsistency that inspired a more extensive hematologic workup, despite the presumed low likelihood of malignancy. This serves as a reminder to think outside of classic “illness scripts” in order to catch uncommon presentations of disease.