Pediatric Chronic Myeloid Leukemia Presenting With Extreme Thrombocytosis Simulating Essential Thrombocythemia

Is very high platelet count always associated with essential thrombocythemia? An unusual presentation in a child

Myeloproliferative neoplasms are rare in childhood. They are categorized as Philadelphia chromosome-positive and Philadelphia chromosome-negative. Chronic myeloid leukemia (CML) is the most common myeloproliferative disease in which the Philadelphia chromosome is detected as a result of BCR-ABL rearrangements. In others, the most common genetic abnormality is JAK2V617F mutation. The coexistence of these 2 abnormalities in CML is unexpected, and rare cases have recently been reported in adults. We present a child who had a very high platelet count in which we found this coexistence. The clinical presentation, laboratory findings, management, and prognosis of this coexistence is challenging in such a rare condition.

Clinical Features and Outcomes of Patients With Chronic Myeloid Leukemia Presenting With Isolated Thrombocytosis: A Systematic Review and a Case From Our Institution

Chronic myeloid leukemia (CML) represents a common condition in the spectrum of myeloproliferative disorders (MPD). It classically exhibits leukocytosis, but rarely presents with isolated thrombocytosis. This paper is designed to review the clinicopathologic features, treatment, and outcomes of patients with CML who present with isolated thrombocytosis. We searched PubMed, MEDLINE®, ScienceDirect, and Scopus for English-language articles about case series and case reports for the period 2000-2020 with the terms "chronic myeloid leukemia" and "thrombocytosis" and pooled them with a case from our institution. Cases were also incorporated from the reference list and screened for inclusion. A total of 20 cases were included in the final cohort. The male-to-female ratio was 1:1.86. The mean age of the patients at the time of initial diagnosis was 40.5 years (range: 9-77 years). Out of 17 cases with available data, seven (41%) were asymptomatic and found to have thrombocytosis incidentally upon routine blood work. Five cases (29.4%) either had a history of thrombotic events or presented with severe thrombotic complications, including ischemic cerebrovascular accidents (CVA), myocardial infarction (MI), pulmonary embolism (PE), and/or miscarriages. Four cases (23.5%) had more than one symptom at presentation, including headache, syncope, and bruising. The average platelet count was 1,923 × 109/L (range: 584-8,688 × 109/L), and one case (5%) had anemia. The bone marrow (BM) examination showed normal cellularity and normal myeloid to erythroid (M/E) ratio in seven (50%) and 11 (84.6%) out of the 14 and 13 cases with reported data, respectively. Moreover, megakaryocytes in the BM were small in 10 cases (71.4%), pleomorphic in three cases (21.4%), and dysplastic in one case (7.1%). Accurate differentiation among MPD subtypes and the exclusion of CML is critical in reaching a proper diagnosis to decide on proper therapy and eventually modify outcomes. Prompt evaluation for the precise diagnosis of patients presenting with isolated marked thrombocytosis will help expedite their diagnosis and initiation of a specific tyrosine kinase inhibitor (TKI) therapy, thereby promptly inducing remission, preventing thrombotic complications, and avoiding adverse drug events, which would eventually improve outcomes.