Clinical and hematological profile and frequency of thromboembolic events in patients with essential thrombocythemia treated at a Peruvian referral hospital.

Abstract

Background: Essential thrombocythemia (ET) is a myeloproliferative neoplasm characterized by persistent thrombocytosis and increased risk of thromboembolic events, which represent the leading cause of morbidity and mortality. JAK2 V617F mutation and classical clinical factors are associated with higher thrombotic risk; however, data from Latin America are limited. Methods: Descriptive observational study including patients diagnosed with ET (WHO 2016 criteria) between January 2020 and December 2024 at Hospital Nacional Edgardo Rebagliati Martins, Lima. Clinical, laboratory, molecular, treatment, and outcome data were collected from electronic medical records. Results: Sixty-three patients were included. Median age was 71 years (IQR 58–80), 58.7% were female. Cardiovascular risk factors were absent in 42.9%; hypertension was the most frequent comorbidity (42.9%). At diagnosis, median platelet count was 802×10⁹/L, leukocytes 8.79×10⁹/L, and hemoglobin 13.5 g/dL. JAK2 mutation was present in 79.4%; only one patient tested CALR-positive, and MPL was not studied. Karyotype was normal in 44.4%, abnormal in 1.6%, and not performed in 53.9%. By IPSET-thrombosis, 74.6% were classified as high risk. During follow-up, 9 patients (14.3%) developed thromboembolic events: 66.7% venous, 22.2% arterial, and 11.1% mixed. Sites included splanchnic (33.3%), lower limbs (33.3%), coronary (22.2%), and jugular (11.1%). One patient progressed to myelofibrosis (1.6%) and one died from thrombosis (1.6%). The most common treatment was aspirin plus hydroxyurea (61.9%). Discussion: Patient demographics (older age, female predominance) were consistent with international reports. JAK2 positivity (79.4%) was higher than the 50–60% reported abroad, likely due to under-testing of CALR/MPL. The high proportion of patients at elevated IPSET-thrombosis risk (74.6%) aligns with the frequent use of cytoreductive therapy. The overall thrombotic rate (14.3%) was within international ranges (11–25%), but venous events predominated, contrasting with most series where arterial events are more common. The presence of unusual sites (splanchnic, jugular) was in line with reports from other myeloproliferative neoplasms. The low rates of transformation and mortality support the generally indolent course of ET, while reaffirming vascular complications as the main threat. Limitations include incomplete MPL and CALR molecular testing. Nevertheless, this study represents one of the first local characterizations of ET in Peru, highlighting the need for broader molecular access and multicenter registries to refine risk stratification and management.