What is pre-fibrotic myelofibrosis and how should it be managed in 2018?

The 2016 World Health Organization (WHO) classification for myeloproliferative neoplasms (MPN) divided myelofibrosis (MF) into pre-fibrotic (pre-MF) and overt-MF categories. This new classification, particularly the entity pre-MF, has been a subject of discussion between experts. Important questions have been raised in recent years, such as the need for bone marrow trephine for diagnosis; how this is interpreted and the weighting given to it in assigning a diagnosis; determination of prognosis for pre-MF patients; including which scoring system to use and, ultimately, an evidence-based management plan for this group of patients. Many pre-MF patients present as young adults, with thrombocytosis, elevated lactate dehydrogenase levels and increased bone marrow fibrosis (i.e. ≥ grade 1). Current management strategies differ in view of age, comorbidities and bone marrow features and the opinion of the managing clinicians. Prognostic scoring systems have some limitations regarding this entity, and at the present time there is limited information about the overall survival and incidence of progression to overt-MF and acute leukaemia for pre-MF. In this clinically focussed article, we review the main characteristics of this new disease category in view of the current published literature and illustrate our discussion with some real patient cases. Lastly, we propose a management strategy for patients to whom this diagnostic label is applied.