Polycythemia vera and essential thrombocythemia in children, still a challenge for pediatricians.

Polycythemia vera (PV) and essential thrombocythemia (ET) are rare myeloproliferative neoplasms (MPN) in children, adolescents and young adults. No recommendations are available concerning these patients' management. Transposing to children the knowledge established in adult patients is not acceptable. For a better understanding of difficulties encountered by pediatricians and adult hematologists, we conducted a national practice analysis concerning follow-up of patients under 18 diagnosed with ET or PV, in France. Then, we present data from a multicentric, descriptive, retrospective study, including 17 patients with ET or PV, diagnosed under 18, coming from 7 hematopediatric departments in France. Interviewed physicians reported a lack of expertise and theoretical training in the hematological field to diagnose and follow children with MPNs. Data from 17 patients (15 ET, 2 PV) confirmed a high proportion of asymptomatic patients at the time of diagnosis (41%). Proportion of "triple-negative" patients (59%) was higher than in adult cohorts. 60% of patients underwent a bone marrow biopsy and 31% of cases were discussed during a multi-disciplinary staff meeting. 76.5% patients were treated, with a high frequency of antithrombotic and cytoreductive drugs. No complications were observed during the 45 months of median follow-up.

Conclusion: Physicians insisted on the need for training. Only the accumulation of descriptions of MPNs in children will lead to a better management of these diseases. Considering the small proportion of pediatric patients with complications after diagnosis, rapid therapeutic de-escalation seems essential to consider during the follow-up in a close collaboration with adult hematologists.

What is known: • Myeloproliferativ neoplams are rare and chronic deseases, most of the time affecting adults but also found in few pediatric patients. • There are no recommendations for the diagnosis, therapeutic management or follow-up of children with polycythemia vera or essential thrombocythemia.

What is new: • Find out how adult haematologists and paediatricians feel about the management and follow-up of paediatric patients with myeloproliferative syndrome through a national practice analysis. • Description of the "real life" follow-up of children with polycythemia vera or essential thrombocythemia in France.