Essential thrombocythemia: a rare disease in childhood
An 8-year-old girl was admitted to our pediatric emergency room complaining of a severe\nheadache but presenting no fever, vomiting, weight loss or any other complaints.\nAccording to her medical history, she had had recurrent episodes of headaches since the\nage of three without any apparent trigger. Ocular and primary neurological causes were\nexcluded.\nUpon admission, the patient presented no cardiorespiratory symptoms. Except for the\nheadache, she had no other neurological symptoms. Her vital signs were as follows: heart\nrate: 96 beats/minute; blood pressure: 100 x 70 mmHg; respiratory rate: 18\nbreaths/minute and temperature: 36ºC. The physical examination revealed\nsplenomegaly (6 cm) in left hypochondrium but no adenopathy. Abdominal ultrasound\nrevealed homogeneous splenomegaly (longitudinal diameter 15 cm) and an angiotomography\nof the central nervous system was normal. Laboratory results were as follows:\nhemoglobin: 12.3 g/dL; hematocrit: 38%; leukocyte count: 28 x 103/µL;\nplatelet count: 1609 x 109/L (confirmed in peripheral blood); analysis of\ncoagulation (prothrombin time, activated partial thromboplastin time, fibrinogen and\nD-dimer), hepatic transaminases, bilirubin and renal function were normal. There was no\nevidence of infection, inflammation, hemolysis or iron deficiency. A hypothetical\ndiagnosis of ET was then proposed and an investigation was undertaken testing platelet\naggregation, bone marrow biopsy, the fusion BCR/ABL protein and the JAK2V617F mutation.\nThe platelet aggregation test showed hyperaggregation with epinephrine, collagen and\nadenosine diphosphate and normal aggregation with ristocetin. The bone marrow biopsy\nshowed megakaryocytic hyperplasia with preserved maturation and atypical megakaryocytes,\nwithout changes in the erythrocyte and granulocyte series. Neither fibrosis nor\ndysplastic changes were observed. The JAK2 mutation (JAK2V617F) was detected in a\nheterozygous status and the expression of BCR/ABL was negative.\nOnce ET diagnosis was confirmed, treatment with aspirin was initiated. The patient\nreceived 100 mg aspirin (3 mg/kg/day) for five months, without response of the\nthrombocytosis and headache symptoms. The aspirin was suspended and low dose hydroxyurea\nwas initiated; dose was increased slowly based on control blood tests. The patient is\ncurrently asymptomatic, having received the drug over six months at a dose of 20\nmg/kg/day. The platelet count started to decrease after 3 months of use, reaching levels\nunder 450 x 109/L.