Spontaneous Resolution of Extreme Essential Thrombocytosis in a Child

Essential Thrombocytosis (ET) is rare in children and its clinical course is considered to be different from the adult disease. Unlike adults, most children with ET do not need treatment; however, children with extreme thrombocytosis present the treating physician with a therapeutic dilemma. We report a girl with a spontaneous resolution of extreme essential thrombocytosis. A 13 year old previously healthy girl presented to our ER with a 3 months history of intermittent mild abdominal pain with short episodes of diarrhea, intermittent episodes of paraesthesia in lower limbs and 3000 × 10⁹/L platelets on CBC with pseudohyperkalemia of 6.4 mEq/L. Physical examination was unremarkable except for some diffuse mild tenderness on abdominal palpation. Laboratory work-up revealed normal WBC and Hb, Platelets 4100 × 10⁹/L, mild microcytosis, Iron - 21.9 mcg/dL, transferin saturation 5.6%, serum potassium − 6.5 mEq/L, LDH 1000 IU. Liver, renal and thyroid function tests were within normal limits. PTT was mildly elevated 49.3 seconds (normal – 24.3–35), LAC-R mildly positive – 1.205 (0.8–1.20), KCT 58.2 sec. Anticardiolipin IgG −4.82 U/ml (negative), IgM - 11.24 U/ml (negative < 7 U/ml). Anti dsDNA and Anti nuclear antibodies were negative. Studies for hypercoagulable state included Protein C, Antitrombin, Factor VIII, IX, XI, Factor V R506Q, and Apolipoprotein a; all were normal. A heterozygosity for PT G20210A was found, as well as homozygosity for MTHFR C667T with a normal level of Homocysteine (7.7mmole/L). Bone marrow aspiration showed increased cellularity of all cell lines, with many young megakaryocytes including some in clusters. No malignant cells were seen. Reticulin score on bone marrow biopsy was 0. Platelets function tests with adenosine di-phosphate and epinephrine were normal. Serum TPO level was 31.0 pg/ml (normal). A karyotype examination revealed a normal 46XX female. FISH for BCR/ABL was negative. DNA mutations for JAK2 on both the 12 and the14 exons and c-mpl mutations were not found. Spontaneous clone formation was normal. Helicobacter pylori IgG was 2.89 U/ml (normal) and stool was negative for parasites. Imaging studies included high resolution abdominal contrast CT scan, upper gastrointestinal tract imaging with gastrografin, Doppler sonography of splanchnic vessels and capsule endoscopy; all were interpreted as normal. Aspirin 75 mg/d was started without antimetabolite therapy. Abdominal pain and diarrhea gradually improved. After 3 month of antiagregant therapy, platelets count declined, gradually but steadily. One year after presentation the child is asymptomatic with platelet count of 600 × 10⁹/L. The spontaneous remission of the extreme ET achieved by conservative treatment with no complications adds to the growing evidence, that childhood ET is a unique entity with different biology than adult ET, which might not need antimetabolite therapy.