Clinical course of myeloproliferative leukaemia virus oncogene (MPL) mutation-associated familial thrombocytosis: a review of 64 paediatric and adult patients.

Familial thrombocytosis (FT) is a rare hereditary haematological disorder characterised by increased platelet count, usually caused by germ-line mutations in thrombopoietin (THPO), myeloproliferative leukaemia virus oncogene (MPL) or Janus kinase 2 (JAK2) genes, and can be associated with increased risk of thrombosis. We aimed to determine the yield of diagnostic tests, assess treatment received and describe the clinical course of MPL-associated FT. We retrospectively reviewed all paediatric and adult haematology patients diagnosed with MPL-related FT, who were seen in our clinics from March 2013 to February 2021. Of 64 eligible patients, 26 (41%) were aged <14 years, while the remaining 38 (59%) patients were adults. The median (interquartile range) age at diagnosis was 20 (33·5) years. In all, 26 tribes were represented in this cohort of 64 patients, out of which 31 (48%) patients belonged to two tribes. A total of 60 patients (94%) had thrombocytosis on blood count. Additional genetic tests, including myelodysplastic syndrome (MDS) gene panel, Philadelphia gene breakpoint cluster region-Abelson (BCR-ABL) and JAK2, were carried out for 52 patients and only one patient was positive for JAK2 mutation. In all, 21 (33%) patients were prescribed aspirin and seven (11%) were prescribed hydroxyurea. Overall, 63 (98%) patients did not develop any thrombotic or haemorrhagic event. There was no significant association of MPL-mutated FT with thrombosis or haemorrhage.